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Hyperthyroidism is the condition that occurs due to excessive production of
thyroid hormone File:Thyroid_system.svg, upright=1.5, The thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobe (anatomy), lobes. The lower two thirds of the lobes are connec ...
s by the
thyroid gland The thyroid, or thyroid gland, is an endocrine gland Endocrine glands are ductless glands of the endocrine system The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organis ...

thyroid gland
. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidism. It is noted that thyrotoxicosis is related to hyper-kinetic movement disorders including chorea and myoclonus. Some, however, use the terms interchangeably. Signs and symptoms vary between people and may include irritability, muscle weakness, sleeping problems, a
fast heartbeat Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the Heart rate#Resting heart rate, normal resting rate. In general, a resting heart rate over 100 pulse, beats per minute is accepted as tachycardia in adults. Heart rates abov ...
,
heat intolerance Heat intolerance is a symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood ...
,
diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery defecation, bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration of ...
, enlargement of the thyroid, hand
tremor A tremor is an involuntary, somewhat rhythmic, muscle contraction Muscle contraction is the activation of tension Tension may refer to: Science * Psychological stress * Tension (physics), a force related to the stretching of an object (the opp ...
, and
weight loss Weight loss, in the context of medicine, health, or , refers to a reduction of the total , by a mean loss of fluid, body fat (), or lean mass (namely bone mineral deposits, muscle, tendon, and other connective tissue). Weight loss can either ...
. Symptoms are typically less severe in the elderly and during
pregnancy Pregnancy, also known as gestation, is the time during which one or more offspring In biology, offspring are the young creation of living organisms, produced either by a Asexual reproduction, single organism or, in the case of sexual repr ...

pregnancy
. An uncommon complication is
thyroid storm Thyroid storm is a rare but severe and potentially life-threatening complication of hyperthyroidism Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormone File:Thyroid_system.svg, upright=1.5, The thyroid ...
in which an event such as an
infection An infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host A host is a person responsible for guests at an event or for providing hospitality during it. Host may ...

infection
results in worsening symptoms such as confusion and a high temperature and often results in death. The opposite is
hypothyroidism Hypothyroidism (also called ''underactive thyroid'', ''low thyroid'' or ''hypothyreosis'') is a disorder of the endocrine system in which the thyroid gland The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two ...

hypothyroidism
, when the thyroid gland does not make enough thyroid hormone.
Graves' disease Graves' disease, also known as toxic diffuse goiter, is an autoimmune disease that affects the thyroid. It frequently results in and is the most common cause of hyperthyroidism. It also often results in an goitre, enlarged thyroid. Signs and sympt ...
is the cause of about 50% to 80% of the cases of hyperthyroidism in the United States. Other causes include
multinodular goiter A goitre, American and British English spelling differences#re er, or goiter, is a swelling in the neck resulting from an enlarged thyroid, thyroid gland. A goitre can be associated with a thyroid that is not functioning properly. Worldwide, over 9 ...
, toxic adenoma, inflammation of the thyroid, eating too much
iodine Iodine is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical ele ...

iodine
, and too much
synthetic thyroid hormone File:Thyroid_system.svg, upright=1.5, The thyroid The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid ...
. A less common cause is a
pituitary adenoma Pituitary adenomas are tumor A neoplasm () is a type of abnormal and excessive growth of tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata ...
. The diagnosis may be suspected based on signs and symptoms and then confirmed with blood tests. Typically blood tests show a low
thyroid stimulating hormone Thyroid-stimulating hormone (also known as thyrotropin, thyrotropic hormone, or abbreviated TSH) is a pituitary hormone that stimulates the thyroid The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two connected ...
(TSH) and raised or .
Radioiodine There are 37 known isotope Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but different numbers of neu ...
uptake by the thyroid, , and TSI antibodies may help determine the cause. Treatment depends partly on the cause and severity of disease. There are three main treatment options:
radioiodine therapy Iodine-131 (131I, I-131) is an important radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is an atom that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: em ...
, medications, and thyroid surgery. Radioiodine therapy involves taking
iodine-131 Iodine-131 (131I, I-131) is an important radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide A nuclide (or nucleide, from nucleus, also known as nuclear species) is a class of atoms characterize ...

iodine-131
by mouth which is then concentrated in and destroys the thyroid over weeks to months. The resulting hypothyroidism is treated with synthetic thyroid hormone. Medications such as
beta blockers Beta blockers (beta-blockers, β-blockers, etc.) are a class of medications that are predominantly used to manage cardiac arrhythmia, abnormal heart rhythms, and to protect the heart from a second heart attack (myocardial infarction) after a firs ...
may control the symptoms, and
anti-thyroid medicationAn antithyroid agent is a hormone antagonist''For the use of hormone antagonists in cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or Metastasis, spread to other parts of the body. These contr ...
s such as
methimazole Thiamazole, also known as methimazole, is a medication used to treat hyperthyroidism Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occ ...

methimazole
may temporarily help people while other treatments are having effect. Surgery to remove the thyroid is another option. This may be used in those with very large thyroids or when cancer is a concern. In the United States hyperthyroidism affects about 1.2% of the population. It occurs between two and ten times more often in women. Onset is commonly between 20 and 50 years of age. Overall the disease is more common in those over the age of 60 years.


Signs and symptoms

Hyperthyroidism may be asymptomatic or present with significant symptoms. Some of the symptoms of hyperthyroidism include nervousness, irritability, increased perspiration, heart racing, hand tremors, anxiety,
trouble sleeping Insomnia, also known as sleeplessness, is a sleep disorder in which people have trouble sleeping. They may have difficulty falling asleep, or staying asleep as long as desired. Insomnia is typically followed by daytime sleepiness, low energy, ir ...

trouble sleeping
, thinning of the skin, fine brittle hair, and muscular weakness—especially in the upper arms and thighs. More frequent bowel movements may occur, and diarrhea is common. Weight loss, sometimes significant, may occur despite a good appetite (though 10% of people with a hyperactive thyroid experience weight gain), vomiting may occur, and, for women, menstrual flow may lighten and menstrual periods may occur less often, or with longer cycles than usual. Thyroid hormone is critical to normal function of cells. In excess, it both overstimulates metabolism and disrupts the normal functioning of
sympathetic nervous system The sympathetic nervous system (SNS) is one of two divisions of the autonomic nervous system The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies smooth muscle ...
, causing "speeding up" of various body systems and symptoms resembling an overdose of
epinephrine Adrenaline, also known as epinephrine, is a hormone A hormone (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a co ...

epinephrine
(adrenaline). These include fast heartbeat and symptoms of
palpitation Palpitations are perceived abnormalities of the heartbeat characterized by awareness of cardiac muscle contractions in the chest, which is further characterized by the hard, fast and/or irregular beatings of the heart. Symptoms include a rapid ...
s, nervous system
tremor A tremor is an involuntary, somewhat rhythmic, muscle contraction Muscle contraction is the activation of tension Tension may refer to: Science * Psychological stress * Tension (physics), a force related to the stretching of an object (the opp ...
such as of the hands and
anxiety Anxiety is an emotion Emotions are mental state, psychological states brought on by neurophysiology, neurophysiological changes, variously associated with thoughts, feelings, behavioural responses, and a degree of pleasure or suffering, disp ...
symptoms, digestive system
hypermotilityGastrointestinal physiology is the branch of human physiology The human body is the structure of a human being Humans (''Homo sapiens'') are the most populous and widespread species In biology, a species is the basic unit of biologic ...
, unintended weight loss, and, in
lipid panel Lipid profile or ''lipid panel'' is a Test panel, panel of blood tests that serves as an initial screening tool for abnormalities in lipids, such as cholesterol and triglycerides. The results of this test can identify certain Inborn error of lipid ...
blood tests, a lower and sometimes unusually low serum
cholesterol Cholesterol is any of a class of certain organic compound, organic molecules. A cholesterol is a sterol (or chemical modification, modified steroid), a type of lipid. Cholesterol is biosynthesis, biosynthesized by all animal Cell (biology)#Euk ...

cholesterol
. Major clinical signs include
weight loss Weight loss, in the context of medicine, health, or , refers to a reduction of the total , by a mean loss of fluid, body fat (), or lean mass (namely bone mineral deposits, muscle, tendon, and other connective tissue). Weight loss can either ...
(often accompanied by an increased
appetite Appetite is the desire to eat Eating (also known as consuming) is the ingestion of food Food is any substance consumed to provide nutritional support for an organism In biology, an organism (from Ancient Greek, Greek: ὀργα ...
), anxiety,
heat intolerance Heat intolerance is a symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood ...
, hair loss (especially of the outer third of the eyebrows), muscle aches, weakness, fatigue, hyperactivity, irritability,
high blood sugar Hyperglycemia is a condition in which an excessive amount of glucose Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy fr ...

high blood sugar
, excessive urination,
excessive thirst Polydipsia is excessive thirst or excess drinking.Porth, C. M. (1990). ''Pathophysiology: Concepts of altered health states''. Philadelphia: J.B. Lippincott Company. The word derives from the Greek language, Greek () "very thirsty", which is deriv ...
,
delirium Delirium (also known as acute confusional state) is an organically caused decline from a previous baseline mental functioning, that develops over a short period of time, typically hours to days. Delirium is a syndrome A syndrome is a set of me ...
,
tremor A tremor is an involuntary, somewhat rhythmic, muscle contraction Muscle contraction is the activation of tension Tension may refer to: Science * Psychological stress * Tension (physics), a force related to the stretching of an object (the opp ...
,
pretibial myxedema Pretibial myxedema (myxoedema (UK), also known as Graves' dermopathy, thyroid dermopathy, Jadassohn-Dösseker disease or Myxoedema tuberosum) is an Infiltration (medical), infiltrative wikt:dermopathy, dermopathy, resulting as a rare complication of ...
(in
Graves' disease Graves' disease, also known as toxic diffuse goiter, is an autoimmune disease that affects the thyroid. It frequently results in and is the most common cause of hyperthyroidism. It also often results in an goitre, enlarged thyroid. Signs and sympt ...
),
emotional lability In medicine and psychology, emotional lability is a sign A sign is an object Object may refer to: General meanings * Object (philosophy), a thing, being, or concept ** Entity, something that is tangible and within the grasp of the sense ...
, and sweating.
Panic attacks Panic attacks are sudden periods of intense fear Fear is an intensely unpleasant emotion in response to perception, perceiving or recognizing a danger or threat. Fear causes physiological changes that may produce behavioral reactions such as ...
, inability to concentrate, and
memory Memory is the faculty of the brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exis ...

memory
problems may also occur.
Psychosis Psychosis is an abnormal condition of the mind that results in difficulties determining what is Reality, real and what is not real. Symptoms may include delusions and hallucinations, among other features. Additional symptoms are thought disord ...
and
paranoia Paranoia is an instinct or thought process that is believed to be heavily influenced by anxiety Anxiety is an emotion Emotions are mental state, psychological states brought on by neurophysiology, neurophysiological changes, variously a ...

paranoia
, common during
thyroid storm Thyroid storm is a rare but severe and potentially life-threatening complication of hyperthyroidism Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormone File:Thyroid_system.svg, upright=1.5, The thyroid ...
, are rare with milder hyperthyroidism. Many persons will experience complete remission of symptoms 1 to 2 months after a
euthyroid The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two connected lobe (anatomy), lobes. The lower two thirds of the lobes are connected by a thin band of Connective tissue, tissue called the thyroid isthmus. The thyroi ...
state is obtained, with a marked reduction in anxiety, sense of exhaustion, irritability, and depression. Some individuals may have an increased rate of anxiety or persistence of
affective Affect, in psychology Psychology is the science of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious mind, unconscious phenomena, as well as feeling and thought. It is an academic discipline of imm ...
and cognitive symptoms for several months to up to 10 years after a euthyroid state is established. In addition, those with hyperthyroidism may present with a variety of physical symptoms such as
palpitations Palpitations are perceived abnormalities of the heartbeat characterized by awareness of cardiac muscle contractions in the chest, which is further characterized by the hard, fast and/or irregular beatings of the heart. Symptoms include a rapid ...
and abnormal heart rhythms (the notable ones being
atrial fibrillation Atrial fibrillation (AF or A-fib) is an abnormal heart rhythm (arrhythmia) characterized by the rapid and irregular beating of the atrial chambers of the heart. It often begins as short periods of abnormal beating, which become longer or con ...

atrial fibrillation
), shortness of breath (
dyspnea Shortness of breath (SOB), also known as dyspnea (BrE British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codificat ...
), loss of
libido Libido (; colloquial Colloquialism or colloquial language is the style (sociolinguistics), linguistic style used for casual (informal) communication. It is the most common functional style of speech, the idiom normally employed in conversation ...
,
amenorrhea Amenorrhea is the absence of a menstrual period The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that make pregnancy possible. The ovarian cyc ...
,
nausea Nausea is a diffuse sensation of unease and discomfort, often perceived as an urge to vomiting, vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, upper abdomen, or ...

nausea
,
vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach The stomach is a muscular, in the of humans and many other animals, including several s. The stomach has a dilat ...

vomiting
,
diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery defecation, bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration of ...
,
gynecomastia Gynecomastia (also spelled gynaecomastia) is the abnormal non-cancerous enlargement of one or both breasts in males due to the growth of breast tissue The breast is one of two prominences located on the upper ventral Standard anatomica ...

gynecomastia
and feminization. Long term untreated hyperthyroidism can lead to
osteoporosis Osteoporosis is a systemic skeletal disorder characterized by low bone massImage:Bone density scanner.jpg, A scanner used to measure bone density using dual energy X-ray absorptiometry Bone density, or bone mineral density (BMD), is the amount ...
. These classical symptoms may not be present often in the elderly. Neurological manifestations can include
tremor A tremor is an involuntary, somewhat rhythmic, muscle contraction Muscle contraction is the activation of tension Tension may refer to: Science * Psychological stress * Tension (physics), a force related to the stretching of an object (the opp ...
s,
chorea Chorea (or choreia, occasionally) is an abnormal involuntary movement disorder Movement disorders are clinical syndromes with either an excess of movement or a paucity of voluntary and involuntary movements, unrelated to weakness or spasticity. ...
,
myopathy In medicine Medicine is the science Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity, awareness, or understanding of someone or something, such as facts ( descriptive knowledge), ...
, and in some susceptible individuals (in particular of Asian descent)
periodic paralysis #REDIRECT Periodic paralysis Periodic paralysis is a group of rare genetic diseases that lead to weakness or paralysis from common triggers such as cold, heat, high carbohydrate meals, not eating, stress or excitement and physical activity of any ...
. An association between thyroid disease and
myasthenia gravis Myasthenia gravis (MG) is a long-term neuromuscular disease A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron A motor neuron (or motoneuron) is a neuron A neuron or nerve cell is an electric ...
has been recognized. The thyroid disease, in this condition, is autoimmune in nature and approximately 5% of people with myasthenia gravis also have hyperthyroidism. Myasthenia gravis rarely improves after thyroid treatment and the relationship between the two entities is not well understood. In
Graves' disease Graves' disease, also known as toxic diffuse goiter, is an autoimmune disease that affects the thyroid. It frequently results in and is the most common cause of hyperthyroidism. It also often results in an goitre, enlarged thyroid. Signs and sympt ...
, ophthalmopathy may cause the eyes to look enlarged because the eye muscles swell and push the eye forward. Sometimes, one or both eyes may bulge. Some have swelling of the front of the neck from an enlarged thyroid gland (a goiter). Minor ocular (eye) signs, which may be present in any type of hyperthyroidism, are eyelid retraction ("stare"),
extraocular muscle The extraocular muscles are the six muscle Muscle is a soft tissue found in most animals. Muscle cells contain protein Proteins are large biomolecules or macromolecules that are comprised of one or more long chains of amino acid residue ...

extraocular muscle
weakness, and lid-lag. In hyperthyroid ''stare'' ( Dalrymple sign) the eyelids are retracted upward more than normal (the normal position is at the superior corneoscleral limbus, where the "white" of the eye begins at the upper border of the iris). Extraocular muscle weakness may present with double vision. In lid-lag ( von Graefe's sign), when the person tracks an object downward with their eyes, the eyelid fails to follow the downward moving iris, and the same type of upper globe exposure which is seen with lid retraction occurs, temporarily. These signs disappear with treatment of the hyperthyroidism. Neither of these ocular signs should be confused with
exophthalmos Exophthalmos (also called exophthalmus, exophthalmia, proptosis, or exorbitism) is a bulging of the eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, a ...
(protrusion of the eyeball), which occurs specifically and uniquely in hyperthyroidism caused by Graves' disease (note that not all exophthalmos is caused by Graves' disease, but when present with hyperthyroidism is diagnostic of Graves' disease). This forward protrusion of the eyes is due to immune-mediated inflammation in the retro-orbital (eye socket) fat. Exophthalmos, when present, may exacerbate hyperthyroid lid-lag and stare.


Thyroid storm

Thyroid storm is a severe form of thyrotoxicosis characterized by rapid and often irregular heart beat, high temperature, vomiting, diarrhea, and mental agitation. Symptoms may not be typical in the young, old, or pregnant. It usually occurs due to untreated hyperthyroidism and can be provoked by infections. It is a
medical emergency A medical emergency is an acute Acute may refer to: Science and technology * Acute angle ** Acute triangle ** Acute, a leaf shape in the glossary of leaf morphology#acute, glossary of leaf morphology * Acute (medicine), a disease that it is o ...

medical emergency
and requires hospital care to control the symptoms rapidly. Even with treatment, death occurs in 20% to 50%.


Hypothyroidism

Hyperthyroidism due to certain types of
thyroiditis Thyroiditis is the inflammation of the thyroid gland The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyr ...

thyroiditis
can eventually lead to
hypothyroidism Hypothyroidism (also called ''underactive thyroid'', ''low thyroid'' or ''hypothyreosis'') is a disorder of the endocrine system in which the thyroid gland The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two ...

hypothyroidism
(a ''lack'' of thyroid hormone), as the thyroid gland is damaged. Also,
radioiodine There are 37 known isotope Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but different numbers of neu ...
treatment of Graves' disease often eventually leads to hypothyroidism. Such hypothyroidism may be diagnosed with thyroid hormone testing and treated by oral thyroid hormone supplementation.


Causes

There are several causes of hyperthyroidism. Most often, the entire gland is overproducing thyroid hormone. Less commonly, a single nodule is responsible for the excess hormone secretion, called a "hot" nodule. Thyroiditis (inflammation of the thyroid) can also cause hyperthyroidism. Functional thyroid tissue producing an excess of thyroid hormone occurs in a number of clinical conditions. The major causes in humans are: *
Graves' disease Graves' disease, also known as toxic diffuse goiter, is an autoimmune disease that affects the thyroid. It frequently results in and is the most common cause of hyperthyroidism. It also often results in an goitre, enlarged thyroid. Signs and sympt ...
. An autoimmune disease (usually, the most common cause with 50–80% worldwide, although this varies substantially with location- i.e., 47% in Switzerland (Horst et al., 1987) to 90% in the USA (Hamburger et al. 1981)). Thought to be due to varying levels of iodine in the diet. It is eight times more common in females than males and often occurs in young females, around 20 – 40 years of age. * Toxic thyroid adenoma (the most common cause in Switzerland, 53%, thought to be atypical due to a low level of dietary iodine in this country) *
Toxic multinodular goiter Toxic multinodular goiter (TMNG), also known as multinodular toxic goiter (MNTG), is an active multinodular goiter associated with hyperthyroidism. It is a common cause of hyperthyroidism in which there is excess production of thyroid hormones fro ...
High blood levels of thyroid hormones (most accurately termed hyperthyroxinemia) can occur for a number of other reasons: *
Inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogen In biology Biology is the natural science that studies life and living organisms, including their anato ...
of the thyroid is called
thyroiditis Thyroiditis is the inflammation of the thyroid gland The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyr ...
. There are several different kinds of thyroiditis including
Hashimoto's thyroiditis Hashimoto's thyroiditis, also known as chronic lymphocytic thyroiditis and Hashimoto's disease, is an autoimmune disease in which the thyroid, thyroid gland is gradually destroyed. Early on, symptoms may not be noticed. Over time, the thyroid m ...

Hashimoto's thyroiditis
(Hypothyroidism immune-mediated), and subacute thyroiditis (de Quervain's). These may be ''initially'' associated with secretion of excess thyroid hormone but usually progress to gland dysfunction and, thus, to hormone deficiency and hypothyroidism. * Oral consumption of excess thyroid hormone tablets is possible (surreptitious use of thyroid hormone), as is the rare event of eating ground beef or pork contaminated with thyroid tissue, and thus thyroid hormones (termed ''hamburger thyrotoxicosis'' or ''alimentary thyrotoxicosis''). Pharmacy compounding errors may also be a cause. *
Amiodarone Amiodarone is an antiarrhythmic medication Antiarrhythmic agents, also known as cardiac dysrhythmia medications, are a group of pharmaceuticals that are used to suppress abnormal rhythms of the heart (cardiac arrhythmias), such as atrial fibrilla ...

Amiodarone
, an antiarrhythmic drug, is structurally similar to thyroxine and may cause either under-or overactivity of the thyroid. * Postpartum thyroiditis (PPT) occurs in about 7% of women during the year after they give birth. PPT typically has several phases, the first of which is hyperthyroidism. This form of hyperthyroidism usually corrects itself within weeks or months without the need for treatment. * A struma ovarii is a rare form of monodermal
teratoma A teratoma is a tumor A neoplasm () is a type of abnormal and excessive growth of tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a ...
that contains mostly thyroid tissue, which leads to hyperthyroidism. * Excess iodine consumption notably from algae such as
kelp Kelps are large brown algae The brown algae (singular: alga), comprising the class (biology), class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Most b ...

kelp
. Thyrotoxicosis can also occur after taking too much thyroid hormone in the form of supplements, such as
levothyroxine Levothyroxine, also known as -thyroxine, is a manufactured form of the thyroid hormone thyroxine (T4). It is used to treat hypothyroidism, thyroid hormone deficiency (hypothyroidism), including Hashimoto's thyroiditis, Hashimoto's disease and a ...
(a phenomenon known as exogenous thyrotoxicosis, alimentary thyrotoxicosis, or
occult The occult, in the broadest sense, is a category of supernatural The supernatural encompasses supposed phenomena or entities that are not subject to the . This term is attributed to , such as s, s, , and . It also includes claimed abiliti ...
factitial thyrotoxicosis). Hypersecretion of
thyroid stimulating hormone Thyroid-stimulating hormone (also known as thyrotropin, thyrotropic hormone, or abbreviated TSH) is a pituitary hormone that stimulates the thyroid The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two connected ...
(TSH), which in turn is almost always caused by a
pituitary adenoma Pituitary adenomas are tumor A neoplasm () is a type of abnormal and excessive growth of tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata ...
, accounts for much less than 1 percent of hyperthyroidism cases.


Diagnosis

Measuring the level of
thyroid-stimulating hormone Thyroid-stimulating hormone (also known as thyrotropin, thyrotropic hormone, or abbreviated TSH) is a pituitary hormone that stimulates the thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the ne ...
(TSH), produced by the pituitary gland (which in turn is also regulated by the hypothalamus's TSH Releasing Hormone) in the blood is typically the initial test for suspected hyperthyroidism. A low TSH level typically indicates that the pituitary gland is being inhibited or "instructed" by the brain to cut back on stimulating the thyroid gland, having sensed increased levels of T4 and/or T3 in the blood. In rare circumstances, a low TSH indicates primary failure of the pituitary, or temporary inhibition of the pituitary due to another illness (
euthyroid sick syndrome Euthyroid sick syndrome (ESS) is a state of adaptation or dysregulation of thyrotropic feedback control wherein the levels of Thyroid hormones, T3 and/or T4 are abnormal, but the thyroid gland does not appear to be dysfunctional. This condition may ...
) and so checking the T4 and T3 is still clinically useful. Measuring specific
antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and Viral disease, viruses. The antibody recognizes a unique mo ...

antibodies
, such as anti-TSH-receptor antibodies in Graves' disease, or anti-thyroid peroxidase in
Hashimoto's thyroiditis Hashimoto's thyroiditis, also known as chronic lymphocytic thyroiditis and Hashimoto's disease, is an autoimmune disease in which the thyroid, thyroid gland is gradually destroyed. Early on, symptoms may not be noticed. Over time, the thyroid m ...

Hashimoto's thyroiditis
—a common cause of
hypothyroidism Hypothyroidism (also called ''underactive thyroid'', ''low thyroid'' or ''hypothyreosis'') is a disorder of the endocrine system in which the thyroid gland The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two ...

hypothyroidism
—may also contribute to the diagnosis. The diagnosis of hyperthyroidism is confirmed by blood tests that show a decreased thyroid-stimulating hormone (TSH) level and elevated T4 and T3 levels. TSH is a hormone made by the pituitary gland in the brain that tells the thyroid gland how much hormone to make. When there is too much thyroid hormone, the TSH will be low. A radioactive iodine uptake test and thyroid scan together characterizes or enables radiologists and doctors to determine the cause of hyperthyroidism. The uptake test uses radioactive iodine injected or taken orally on an empty stomach to measure the amount of iodine absorbed by the thyroid gland. Persons with hyperthyroidism absorb much more iodine than healthy persons which includes radioactive iodine which is easy to measure. A thyroid scan producing images is typically conducted in connection with the uptake test to allow visual examination of the over-functioning gland. Thyroid
scintigraphy Scintigraphy (from Latin ''scintilla'', "spark"), also known as a gamma scan, is a diagnostic test in nuclear medicine Nuclear medicine is a medical specialty A medical specialty is a branch of medical practice that is focused on a defined gro ...
is a useful test to characterize (distinguish between causes of) hyperthyroidism, and this entity from thyroiditis. This test procedure typically involves two tests performed in connection with each other: an iodine uptake test and a scan (imaging) with a
gamma camera A gamma camera (γ-camera), also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy Scintigraphy (from Latin ''scintilla'', "spark"), also known as a ...

gamma camera
. The uptake test involves administering a dose of radioactive iodine (radioiodine), traditionally
iodine-131 Iodine-131 (131I, I-131) is an important radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide A nuclide (or nucleide, from nucleus, also known as nuclear species) is a class of atoms characterize ...

iodine-131
(131I), and more recently
iodine-123 Iodine-123 (123I) is a radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus The atomic nucleus is the small ...

iodine-123
(123I).
Iodine-123 Iodine-123 (123I) is a radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus The atomic nucleus is the small ...

Iodine-123
may be the preferred radionuclide in some clinics due to its more favorable radiation
dosimetry Radiation dosimetry in the fields of health physics Health physics, also referred to as the science of radiation protection Radiation protection, also known as radiological protection, is defined by the International Atomic Energy Agency Th ...
(i.e. less radiation dose to the person per unit administered radioactivity) and a gamma photon energy more amenable to imaging with the
gamma camera A gamma camera (γ-camera), also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy Scintigraphy (from Latin ''scintilla'', "spark"), also known as a ...

gamma camera
. For the imaging scan, I-123 is considered an almost ideal isotope of iodine for imaging thyroid tissue and thyroid cancer metastasis. Typical administration involves a pill or liquid containing sodium iodide (NaI) taken orally, which contains a small amount of
iodine-131 Iodine-131 (131I, I-131) is an important radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide A nuclide (or nucleide, from nucleus, also known as nuclear species) is a class of atoms characterize ...

iodine-131
, amounting to perhaps less than a grain of salt. A 2-hour fast of no food prior to and for 1 hour after ingesting the pill is required. This low dose of radioiodine is typically tolerated by individuals otherwise allergic to iodine (such as those unable to tolerate contrast mediums containing larger doses of iodine such as used in
CT scan A CT scan or computed tomography scan (formerly known as computed axial tomography or CAT scan) is a medical image, imaging Scientific technique, technique used in radiology to obtain detailed internal images of the body noninvasively for Diagno ...
,
intravenous pyelogram Pyelogram (or pyelography or urography) is a form of imaging of the renal pelvis The renal pelvis or pelvis of the kidney is the funnel-like dilated part of the ureter in the kidney. In humans, the renal pelvis is the point where the two or three Re ...
(IVP), and similar imaging diagnostic procedures). Excess radioiodine that does not get absorbed into the thyroid gland is eliminated by the body in urine. Some people with hyperthyroidism may experience a slight allergic reaction to the diagnostic radioiodine and may be given an
antihistamine Antihistamines are drugs Uncoated tablets, consisting of about 90% acetylsalicylic acid, along with a minor amount of inert fillers and binders. Aspirin is a pharmaceutical drug often used to treat pain, fever, and inflammation. A drug i ...

antihistamine
. The person returns 24 hours later to have the level of radioiodine "uptake" (absorbed by the thyroid gland) measured by a device with a metal bar placed against the neck, which measures the radioactivity emitting from the thyroid. This test takes about 4 minutes while the uptake % (''i.e.,'' percentage) is accumulated (calculated) by the machine software. A scan is also performed, wherein images (typically a center, left and right angle) are taken of the contrasted thyroid gland with a
gamma camera A gamma camera (γ-camera), also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy Scintigraphy (from Latin ''scintilla'', "spark"), also known as a ...

gamma camera
; a
radiologist Radiology is the medical discipline that uses medical imaging Medical imaging is the technique and process of imaging Imaging is the representation or reproduction of an object's form; especially a visual representation (i.e., the form ...
will read and prepare a report indicating the uptake % and comments after examining the images. People with hyperthyroid will typically "take up" higher than normal levels of radioiodine. Normal ranges for RAI uptake are from 10 to 30%. In addition to testing the TSH levels, many doctors test for T3, Free T3, T4, and/or Free T4 for more detailed results. Free T4 is unbound to any protein in the blood. Adult limits for these hormones are: TSH (units): 0.45 – 4.50 uIU/mL; T4 Free/Direct (nanograms): 0.82 – 1.77 ng/dl; and T3 (nanograms): 71 – 180 ng/dl. Persons with hyperthyroidism can easily exhibit levels many times these upper limits for T4 and/or T3. See a complete table of normal range limits for thyroid function at the
thyroid gland The thyroid, or thyroid gland, is an endocrine gland Endocrine glands are ductless glands of the endocrine system The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organis ...

thyroid gland
article. In hyperthyroidism CK-MB (
Creatine kinase Creatine kinase (CK), also known as creatine phosphokinase (CPK) or phosphocreatine kinase, is an enzyme () expressed by various tissues and cell types. CK catalyses the conversion of creatine and uses adenosine triphosphate (ATP) to create phospho ...
) is usually elevated. File:Hyperthyroidism (1).jpg File:Hyperthyroidism (2).jpg File:Hyperthyroidism (3).jpg


Subclinical

In overt primary hyperthyroidism, TSH levels are low and T4 and T3 levels are high. Subclinical hyperthyroidism is a milder form of hyperthyroidism characterized by low or undetectable serum TSH level, but with a normal serum free thyroxine level. Although the evidence for doing so is not definitive, treatment of elderly persons having subclinical hyperthyroidism could reduce the number of cases of
atrial fibrillation Atrial fibrillation (AF or A-fib) is an abnormal heart rhythm (arrhythmia) characterized by the rapid and irregular beating of the atrial chambers of the heart. It often begins as short periods of abnormal beating, which become longer or con ...

atrial fibrillation
. There is also an increased risk of bone fractures (by 42%) in people with subclinical hyperthyroidism; there is insufficient evidence to say whether treatment with antithyroid medications would reduce that risk.


Screening

In those without symptoms who are not pregnant there is little evidence for or against screening.


Treatment


Antithyroid drugs

Thyrostatics (Antithyroid agent, antithyroid drugs) are drugs that inhibit the production of thyroid hormones, such as carbimazole (used in the UK) and
methimazole Thiamazole, also known as methimazole, is a medication used to treat hyperthyroidism Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occ ...

methimazole
(used in the US, Germany and Russia), and propylthiouracil. Thyrostatics are believed to work by inhibiting the iodination of thyroglobulin by thyroperoxidase and, thus, the formation of tetraiodothyronine (T4). Propylthiouracil also works outside the thyroid gland, preventing the conversion of (mostly inactive) T4 to the active form T3. Because thyroid tissue usually contains a substantial reserve of thyroid hormone, thyrostatics can take weeks to become effective and the dose often needs to be carefully titrated over a period of months, with regular doctor visits and blood tests to monitor results. A very high dose is often needed early in treatment, but, if too high a dose is used persistently, people can develop symptoms of hypothyroidism. This titrating of the dose is difficult to do accurately, and so sometimes a "block and replace" attitude is taken. In block and replace treatments thyrostatics are taken in sufficient quantities to completely block thyroid hormones, and the person treated as though they have complete hypothyroidism.


Beta-blockers

Many of the common symptoms of hyperthyroidism such as palpitations, trembling, and anxiety are mediated by increases in beta-adrenergic receptors on cell surfaces. Beta blockers, typically used to treat high blood pressure, are a class of drugs that offset this effect, reducing rapid pulse associated with the sensation of palpitations, and decreasing tremor and anxiety. Thus, a person suffering from hyperthyroidism can often obtain immediate temporary relief until the hyperthyroidism can be characterized with the Radioiodine test noted above and more permanent treatment take place. Note that these drugs do not treat hyperthyroidism or any of its long-term effects if left untreated, but, rather, they treat or reduce only symptoms of the condition. Some minimal effect on thyroid hormone production however also comes with propranolol—which has two roles in the treatment of hyperthyroidism, determined by the different isomers of propranolol. L-propranolol causes beta-blockade, thus treating the symptoms associated with hyperthyroidism such as tremor, palpitations, anxiety, and
heat intolerance Heat intolerance is a symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood ...
. D-propranolol inhibits thyroxine deiodinase, thereby blocking the conversion of T4 to T3, providing some though minimal therapeutic effect. Other beta-blockers are used to treat only the symptoms associated with hyperthyroidism. Propranolol in the UK, and metoprolol in the US, are most frequently used to augment treatment for people with hyperthyroid .


Diet

People with autoimmune hyperthyroidism (such as in Graves' disease, Grave's disease) should not eat foods high in iodine, such as edible seaweed and
kelp Kelps are large brown algae The brown algae (singular: alga), comprising the class (biology), class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Most b ...

kelp
s. From a public health perspective, the general introduction of iodized salt in the United States in 1924 resulted in lower disease, goiters, as well as improving the lives of children whose mothers would not have eaten enough iodine during pregnancy which would have lowered the IQs of their children.


Surgery

Surgery (thyroidectomy to remove the whole thyroid or a part of it) is not extensively used because most common forms of hyperthyroidism are quite effectively treated by the radioactive iodine method, and because there is a risk of also removing the parathyroid glands, and of cutting the recurrent laryngeal nerve, making swallowing difficult, and even simply generalized staphylococcus, staphylococcal infection as with any major surgery. Some people with Graves' may opt for surgical intervention. This includes those that cannot tolerate medicines for one reason or another, people that are allergic to iodine, or people that refuse radioiodine. If people have toxic nodules treatments typically include either removal or injection of the nodule with alcohol.


Radioiodine

In
iodine-131 Iodine-131 (131I, I-131) is an important radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide A nuclide (or nucleide, from nucleus, also known as nuclear species) is a class of atoms characterize ...

iodine-131
(
radioiodine There are 37 known isotope Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but different numbers of neu ...
) Radiation therapy#Radioisotope and therapy (RIT), radioisotope therapy, which was first pioneered by Dr. Saul Hertz,Hertz, Barbara, Schuleller, Kristin, Saul Hertz, MD (1905–1950) A Pioneer in the Use of Radioactive Iodine, ''Endocrine Practice'' 2010 16,4;713–715. radioactive iodine-131 is given orally (either by pill or liquid) on a one-time basis, to severely restrict, or altogether destroy the function of a hyperactive thyroid gland. This isotope of radioactive iodine used for ablative treatment is more potent than diagnostic radioiodine (usually
iodine-123 Iodine-123 (123I) is a radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus The atomic nucleus is the small ...

iodine-123
or a very low amount of iodine-131), which has a biological half-life from 8–13 hours. Iodine-131, which also emits beta particles that are far more damaging to tissues at short range, has a half-life of approximately 8 days. People not responding sufficiently to the first dose are sometimes given an additional radioiodine treatment, at a larger dose. Iodine-131 in this treatment is picked up by the active cells in the thyroid and destroys them, rendering the thyroid gland mostly or completely inactive. Since iodine is picked up more readily (though not exclusively) by thyroid cells, and (more important) is picked up even more readily by over-active thyroid cells, the destruction is local, and there are no widespread side effects with this therapy. Radioiodine ablation has been used for over 50 years, and the only major reasons for not using it are pregnancy and breastfeeding (Breast, breast tissue also picks up and concentrates iodine). Once the thyroid function is reduced, replacement hormone therapy (
levothyroxine Levothyroxine, also known as -thyroxine, is a manufactured form of the thyroid hormone thyroxine (T4). It is used to treat hypothyroidism, thyroid hormone deficiency (hypothyroidism), including Hashimoto's thyroiditis, Hashimoto's disease and a ...
) taken orally each day replaces the thyroid hormone that is normally produced by the body. There is extensive experience, over many years, of the use of radioiodine in the treatment of thyroid overactivity and this experience does not indicate any increased risk of thyroid cancer following treatment. However, a study from 2007 has reported an increased number of cancer cases after radioiodine treatment for hyperthyroidism. The principal advantage of radioiodine treatment for hyperthyroidism is that it tends to have a much higher success rate than medications. Depending on the dose of radioiodine chosen, and the disease under treatment (Graves' vs. toxic goiter, vs. hot nodule etc.), the success rate in achieving definitive resolution of the hyperthyroidism may vary from 75 to 100%. A major expected side-effect of radioiodine in people with Graves' disease is the development of lifelong
hypothyroidism Hypothyroidism (also called ''underactive thyroid'', ''low thyroid'' or ''hypothyreosis'') is a disorder of the endocrine system in which the thyroid gland The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two ...

hypothyroidism
, requiring daily treatment with thyroid hormone. On occasion, some people may require more than one radioactive treatment, depending on the type of disease present, the size of the thyroid, and the initial dose administered. People with Graves' disease manifesting moderate or severe Graves' ophthalmopathy are cautioned against radioactive iodine-131 treatment, since it has been shown to exacerbate existing thyroid eye disease. People with mild or no ophthalmic symptoms can mitigate their risk with a concurrent six-week course of prednisone. The mechanisms proposed for this side effect involve a TSH receptor common to both thyroid epithelial cell, thyrocytes and retro-orbital tissue. As radioactive iodine treatment results in the destruction of thyroid tissue, there is often a transient period of several days to weeks when the symptoms of hyperthyroidism may actually worsen following radioactive iodine therapy. In general, this happens as a result of thyroid hormones being released into the blood following the radioactive iodine-mediated destruction of thyroid cells that contain thyroid hormone. In some people, treatment with medications such as beta blockers (propranolol, atenolol, etc.) may be useful during this period of time. Most people do not experience any difficulty after the radioactive iodine treatment, usually given as a small pill. On occasion, neck tenderness or a sore throat may become apparent after a few days, if moderate inflammation in the thyroid develops and produces discomfort in the neck or throat area. This is usually transient, and not associated with a fever, etc. Women breastfeeding should discontinue breastfeeding for at least a week, and likely longer, following radioactive iodine treatment, as small amounts of radioactive iodine may be found in breast milk even several weeks after the radioactive iodine treatment. A common outcome following radioiodine is a swing from hyperthyroidism to the easily treatable hypothyroidism, which occurs in 78% of those treated for Graves' thyrotoxicosis and in 40% of those with toxic multinodular goiter or solitary toxic adenoma. Use of higher doses of radioiodine reduces the number of cases of treatment failure, with penalty for higher response to treatment consisting mostly of higher rates of eventual hypothyroidism which requires hormone treatment for life. There is increased sensitivity to radioiodine therapy in thyroids appearing on Medical ultrasonography, ultrasound scans as more uniform (hypoechogenic), due to densely packed large cells, with 81% later becoming hypothyroid, compared to just 37% in those with more normal scan appearances (normoechogenic).


Thyroid storm

Thyroid storm presents with extreme symptoms of hyperthyroidism. It is treated aggressively with resuscitation measures along with a combination of the above modalities including: an intravenous beta blockers such as propranolol, followed by a thioamide such as
methimazole Thiamazole, also known as methimazole, is a medication used to treat hyperthyroidism Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occ ...

methimazole
, an iodinated radiocontrast agent or an iodine solution if the radiocontrast agent is not available, and an intravenous steroid such as hydrocortisone.


Alternative medicine

In countries such as China, herbs used alone or with antithyroid medications are used to treat hyperthyroidism. Very low quality evidence suggests that Chinese herbology, traditional Chinese herbal medications may be beneficial when taken along with routine hyperthyroid medications, however, there is no reliable evidence to determine the effectiveness of Chinese herbal medications.for treating hyperthyroidism.


Epidemiology

In the United States hyperthyroidism affects about 1.2% of the population. About half of these cases have obvious symptoms while the other half do not. It occurs between two and ten times more often in women. The disease is more common in those over the age of 60 years. Signs and symptoms of Graves' disease#Subclinical hyperthyroidism, Subclinical hyperthyroidism modestly increases the risk of cognitive impairment and dementia.


History

Caleb Hillier Parry first made the association between the goiter and protrusion of the eyes in 1786, however, did not publish his findings until 1825. In 1835, Irish doctor Robert James Graves discovered a link between the protrusion of the eyes and goiter, giving his name to the autoimmune disease now known as Graves' Disease.


Pregnancy

Recognizing and evaluating hyperthyroidism in pregnancy is a diagnostic challenge. Thyroid hormones are naturally elevated during pregnancy and hyperthyroidism must also be distinguished from gestational transient thyrotoxicosis. Nonetheless, high maternal FT4 levels during pregnancy have been associated with impaired brain developmental outcomes of the offspring and this was independent of for example hCG levels.


Other animals


Cats

Hyperthyroidism is one of the most common endocrine conditions affecting older domesticated cat, housecats. In the United States, up to 10% of cats over ten years old have hyperthyroidism. The disease has become significantly more common since the first reports of feline hyperthyroidism in the 1970s. The most common cause of hyperthyroidism in cats is the presence of benign tumors called adenomas. 98% of cases are caused by the presence of an adenoma, but the reason these cats develop such tumors continues to be studied. The most common presenting symptoms are: rapid
weight loss Weight loss, in the context of medicine, health, or , refers to a reduction of the total , by a mean loss of fluid, body fat (), or lean mass (namely bone mineral deposits, muscle, tendon, and other connective tissue). Weight loss can either ...
, tachycardia (rapid heart rate),
vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach The stomach is a muscular, in the of humans and many other animals, including several s. The stomach has a dilat ...

vomiting
,
diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery defecation, bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration of ...
, increased consumption of fluids (polydipsia), increased appetite (polyphagia), and increased urine production (polyuria). Other symptoms include hyperactivity, possible aggression, an unkempt appearance, and large, thick claws. Heart murmurs and a gallop rhythm can develop due to secondary hypertrophic cardiomyopathy. About 70% of afflicted cats also have enlarged thyroid glands (goiter). 10% of cats exhibit "apathetic hyperthyroidism", which is characterized by anorexia and lethargy. The same three treatments used with humans are also options in treating feline hyperthyroidism (surgery, radioiodine treatment, and anti-thyroid drugs). There is also a special low iodine diet available that will control the symptoms providing no other food is fed; Hill's y/d formula, when given exclusively, decreases T4 production by limiting the amount of iodine needed for thyroid hormone production. It is the only available commercial diet that focuses on managing feline hyperthyroidism. Medical and dietary management using methimazole and Hill's y/d cat food will give hyperthyroid cats an average of 2 years before dying due to secondary conditions such as heart and kidney failure. Drugs used to help manage the symptoms of hyperthyroidism are methimazole and carbimazole. Drug therapy is the least expensive option, even though the drug must be administered daily for the remainder of the cat's life. Carbimazole is only available as a once daily tablet. Methimazole is available as an oral solution, a tablet, and compounded as a topical medication, topical gel that is applied using a finger cot to the hairless skin inside a cat's ear. Many cat owners find this gel a good option for cats that don't like being given pills. Radioiodine treatment, however, is not available in all areas, as this treatment requires nuclear radiological expertise and facilities that not only board the cat, but are specially equipped to manage the cat's urine, sweat, saliva, and stool, which are radioactive for several days after the treatment, usually for a total of 3 weeks (the cat spends the first week in total isolation and the next two weeks in close confinement). In the United States, the guidelines for radiation levels vary from state to state; some states such as Massachusetts allow hospitalization for as little as two days before the animal is sent home with care instructions.


Dogs

Hyperthyroidism is much less common in dogs compared to cats. Hyperthyroidism may be caused by a thyroid tumor. This may be a thyroid carcinoma. About 90% of carcinomas are very aggressive; they invade the surrounding tissues and Metastasis, metastasize (spread) to other tissues, particularly the lungs. This has a poor prognosis. Surgery to remove the tumor is often very difficult due to metastasis into arteries, the esophagus, or the windpipe. It may be possible to reduce the size of the tumor, thus relieving symptoms and allowing time for other treatments to work. About 10% of thyroid tumors are benign; these often cause few symptoms. In dogs treated for
hypothyroidism Hypothyroidism (also called ''underactive thyroid'', ''low thyroid'' or ''hypothyreosis'') is a disorder of the endocrine system in which the thyroid gland The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two ...

hypothyroidism
(lack of thyroid hormone), iatrogenic hyperthyroidism may occur as a result of an overdose of the thyroid hormone replacement medication,
levothyroxine Levothyroxine, also known as -thyroxine, is a manufactured form of the thyroid hormone thyroxine (T4). It is used to treat hypothyroidism, thyroid hormone deficiency (hypothyroidism), including Hashimoto's thyroiditis, Hashimoto's disease and a ...
; in this case, treatment involves reducing the dose of levothyroxine. Dogs which display coprophagy, the consumption of feces, and also live in a household with a dog receiving levothyroxine treatment, may develop hyperthyroidism if they frequently eat the feces from the dog receiving levothyroxine treatment. Hyperthyroidism may occur if a dog eats an excessive amount of thyroid gland tissue. This has occurred in dogs fed commercial dog food.


See also

* High-output cardiac failure * Jod-Basedow phenomenon


References


External links


Merck Manual article about hyperthyroidism
* * Brent, Gregory A. (Ed.)
''Thyroid Function Testing''
New York : Springer, Series: Endocrine Updates, Vol. 28, 1st Edition., 2010. * * {{Thyroid disease Thyroid disease Endocrine-related cutaneous conditions Dog diseases Thyroid Cat diseases Wikipedia medicine articles ready to translate Wikipedia emergency medicine articles ready to translate