Polydipsia is excessive

thirst Thirst is the craving for potable fluids, resulting in the basic instinct of animals to drink. It is an essential mechanism involved in fluid balance. It arises from a lack of fluids or an increase in the concentration of certain osmolites, suc ...

or excess drinking.Porth, C. M. (1990). ''Pathophysiology: Concepts of altered health states''. Philadelphia: J.B. Lippincott Company. The word derives from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

() "very thirsty", which is derived from (, "much, many") + (, "thirst"). Polydipsia is a nonspecific

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 pressure or an abnormality showin ...

in various medical disorders. It also occurs as an abnormal behaviour in some non-human animals, such as in birds.

Causes

Diabetes

Polydipsia can be characteristic of

diabetes mellitus Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...

, often as an initial symptom. It is observed in cases of poorly controlled diabetes, which is sometimes the result of low patient adherence to

anti-diabetic medication Drugs used in diabetes treat diabetes mellitus by altering the glucose level in the blood. With the exceptions of insulin, most GLP receptor agonists ( liraglutide, exenatide, and others), and pramlintide, all are administered orally and are th ...

Diabetes insipidus Diabetes insipidus (DI), recently renamed to Arginine Vasopressin Deficiency (AVP-D) and Arginine Vasopressin Resistance (AVP-R), is a condition characterized by large amounts of dilute urine and increased thirst. The amount of urine produce ...

("tasteless" diabetes, as opposed to diabetes mellitus) can also cause polydipsia.

Other physiological causes

It can also be caused by a change in the

osmolality Molality is a measure of the number of moles of solute in a solution corresponding to 1 kg or 1000 g of solvent. This contrasts with the definition of molarity which is based on a specified volume of solution. A commonly used unit for molali ...

of the

extracellular fluid In cell biology, extracellular fluid (ECF) denotes all body fluid outside the cells of any multicellular organism. Total body water in healthy adults is about 60% (range 45 to 75%) of total body weight; women and the obese typically have a low ...

s of the body,

hypokalemia Hypokalemia is a low level of potassium (K+) in the blood serum. Mild low potassium does not typically cause symptoms. Symptoms may include feeling tired, leg cramps, weakness, and constipation. Low potassium also increases the risk of an abno ...

, decreased blood volume (as occurs during major

hemorrhage Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, vag ...

), and other conditions that create a water deficit. This is usually a result of

osmotic diuresis Diuresis () is increased urination (polyuria) or, in the related word senses more often intended, the physiological process that produces such an increase or the administration of medications to encourage that process. It involves extra urine pro ...

. Polydipsia is also a symptom of

anticholinergic Anticholinergics (anticholinergic agents) are substances that block the action of the neurotransmitter called acetylcholine (ACh) at synapses in the central and peripheral nervous system. These agents inhibit the parasympathetic nervous system ...

poisoning. Zinc is also known to reduce symptoms of polydipsia by causing the body to absorb fluids more efficiently (reduction of diarrhea, induces constipation) and it causes the body to retain more sodium; thus a zinc deficiency can be a possible cause. The combination of polydipsia and (nocturnal)

polyuria Polyuria () is excessive or an abnormally large production or passage of urine (greater than 2.5 L or 3 L over 24 hours in adults). Increased production and passage of urine may also be termed diuresis. Polyuria often appears in conjunction wit ...

is also seen in (primary) hyperaldosteronism (which often goes with hypokalemia).

Antipsychotics Antipsychotics, also known as neuroleptics, are a class of Psychiatric medication, psychotropic medication primarily used to manage psychosis (including delusions, hallucinations, paranoia or disordered thought), principally in schizophrenia but ...

can have side effects such as

dry mouth Xerostomia, also known as dry mouth, is dryness in the mouth, which may be associated with a change in the composition of saliva, or reduced salivary flow, or have no identifiable cause. This symptom is very common and is often seen as a side eff ...

that may make the patient feel thirsty.

Primary polydipsia

Primary polydipsia describes excessive thirst and water intake caused in the absence of physiological stimuli to drink. This includes both psychogenic primary polydipsia and non-psychogenic primary polydipsia, such as in patients with autoimmune chronic hepatitis with severely elevated

globulin The globulins are a family of globular proteins that have higher molecular weights than albumins and are insoluble in pure water but dissolve in dilute salt solutions. Some globulins are produced in the liver, while others are made by the immune ...

levels. Psychogenic polydipsia is an excessive water intake seen in some patients with mental illnesses such as

schizophrenia Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social withdra ...

, or with developmental disabilities. It should be taken very seriously, as the amount of water ingested exceeds the amount that can be excreted by the kidneys, and can on rare occasions be life-threatening as the body's

serum sodium Sodium ions (Na) are necessary in small amounts for some types of plants, but sodium as a nutrient is more generally needed in larger amounts by animals, due to their use of it for generation of nerve impulses and for maintenance of electrolyte ...

level is diluted to an extent that seizures and cardiac arrest can occur. While psychogenic polydipsia is generally not found outside the population of serious mental disorders, there is some anecdotal evidence of a milder form (typically called 'habit polydipsia' or 'habit drinking') that can be found in the absence of psychosis or other mental conditions. The excessive levels of fluid intake may result in a false diagnosis of

diabetes insipidus Diabetes insipidus (DI), recently renamed to Arginine Vasopressin Deficiency (AVP-D) and Arginine Vasopressin Resistance (AVP-R), is a condition characterized by large amounts of dilute urine and increased thirst. The amount of urine produce ...

, since the chronic ingestion of excessive water can produce diagnostic results that closely mimic those of mild diabetes insipidus. As discussed in the entry on

, "Habit drinking (in its severest form termed psychogenic polydipsia) is the most common imitator of diabetes insipidus at all ages. While many adult cases in the medical literature are associated with mental disorders, most patients with habit polydipsia have no other detectable disease. The distinction is made during the water deprivation test, as some degree of urinary concentration above isosmolar is usually obtained before the patient becomes dehydrated." However, prior to a water deprivation test, consideration should be given to a psychiatric consult to see whether it is possible to rule out psychogenic polydipsia or habit polydipsia.

Diagnosis

Polydipsia is a symptom (evidence of a disease state), not a disease in itself. As it is often accompanied by

(excessive urination) and low sodium levels. Investigations directed at diagnosing

and

can be useful. Blood serum tests can also provide useful information about the osmolality of the body's extracellular fluids. A decrease in osmolality caused by excess water intake will decrease the serum concentration of

red blood cells Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek language, Greek ''erythros'' for "red" and ''k ...

, blood urea nitrogen (BUN), and sodium.

References

External links

{{General symptoms and signs Symptoms and signs: Endocrinology, nutrition, and metabolism Thirst