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Parathyroid Hormone
Parathyroid hormone (PTH), also called parathormone or parathyrin, is a peptide hormone secreted by the parathyroid glands that regulates the serum calcium concentration through its effects on bone, kidney, and intestine. PTH influences bone remodeling, which is an ongoing process in which bone tissue is alternately resorbed and rebuilt over time. PTH is secreted in response to low blood serum calcium (Ca2+) levels. PTH indirectly stimulates osteoclast activity within the bone matrix ( osteon), in an effort to release more ionic calcium (Ca2+) into the blood to elevate a low serum calcium level. The bones act as a (metaphorical) "bank of calcium" from which the body can make "withdrawals" as needed to keep the amount of calcium in the blood at appropriate levels despite the ever-present challenges of metabolism, stress, and nutritional variations. PTH is "a key that unlocks the bank vault" to remove the calcium. PTH is secreted primarily by the chief cells of the par ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hormone
A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required for the correct development of animals, plants and fungi. Due to the broad definition of a hormone (as a signaling molecule that exerts its effects far from its site of production), numerous kinds of molecules can be classified as hormones. Among the substances that can be considered hormones, are eicosanoids (e.g. prostaglandins and thromboxanes), steroids (e.g. oestrogen and brassinosteroid), amino acid derivatives (e.g. epinephrine and auxin), protein or peptides (e.g. insulin and CLE peptides), and gases (e.g. ethylene and nitric oxide). Hormones are used to communicate between organs and tissues. In vertebrates, hormones are responsible for regulating a variety of physiological processes and behavioral activities such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parathyroid Chief Cell
Parathyroid chief cells (also called parathyroid principal cells or simply parathyroid cells, C-cells, or parafollicular cells) are one of the two cell types of the parathyroid glands, along with oxyphil cells. The chief cells are much more prevalent in the parathyroid gland than the oxyphil cells. It is perceived that oxyphil cells may be derived from chief cells at puberty, as they are not present at birth like chief cells. Most individuals display four parathyroid glands adjacent to the thyroid gland anterior in the neck. Histology The chief cells are organized as dense cords surrounding the capillaries in the parathyroid. Chief cells appear as a dark purple in an H&E stain, with the oxyphil cells staining as a lighter pink. They are polygonal in shape with a round nucleus. Chief cells spend most time inactive due to normal calcium level conditions. These inactive cells are classified as cuboidal. They have low levels of secretory granules, as opposed to active chief cell ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypercalcemia
Hypercalcemia, also spelled hypercalcaemia, is a high calcium (Ca2+) level in the blood serum. The normal range is 2.1–2.6 mmol/L (8.8–10.7 mg/dL, 4.3–5.2 mEq/L), with levels greater than 2.6 mmol/L defined as hypercalcemia. Those with a mild increase that has developed slowly typically have no symptoms. In those with greater levels or rapid onset, symptoms may include abdominal pain, bone pain, confusion, depression, weakness, kidney stones or an abnormal heart rhythm including cardiac arrest. Most outpatient cases are due to primary hyperparathyroidism and inpatient cases due to cancer. Other causes of hypercalcemia include sarcoidosis, tuberculosis, Paget disease, multiple endocrine neoplasia (MEN), vitamin D toxicity, familial hypocalciuric hypercalcaemia and certain medications such as lithium and hydrochlorothiazide. Diagnosis should generally include either a corrected calcium or ionized calcium level and be confirmed after a week. Specif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypocalcemia
Hypocalcemia is a medical condition characterized by low calcium levels in the blood serum. The normal range of blood calcium is typically between 2.1–2.6 mmol/L (8.8–10.7 mg/dL, 4.3–5.2 mEq/L) while levels less than 2.1 mmol/L are defined as hypocalcemic. Mildly low levels that develop slowly often have no symptoms. Otherwise symptoms may include numbness, muscle spasms, seizures, confusion, or cardiac arrest. The most common cause for hypocalcemia is iatrogenic hypoparathyroidism. Other causes include other forms of hypoparathyroidism, vitamin D deficiency, kidney failure, pancreatitis, calcium channel blocker overdose, rhabdomyolysis, tumor lysis syndrome, and medications such as bisphosphonates or denosumab. Diagnosis should generally be confirmed with a corrected calcium or ionized calcium level. Specific changes may be seen on an electrocardiogram (ECG). Initial treatment for severe disease is with intravenous calcium chloride and possibly mag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bone Disease
Bone disease refers to the medical conditions which affect the bone. Terminology A bone disease is also called an "osteopathy", but because the term osteopathy is often used to refer to an alternative health-care philosophy, use of the term can cause some confusion. Bone and cartilage disorders Osteochondrodysplasia is a general term for a disorder of the development of bone and cartilage. List A * Ambe * Avascular necrosis or Osteonecrosis * Arthritis B * Bone spur (Osteophytes) C * Craniosynostosis * Coffin–Lowry syndrome * Copenhagen disease F * Fibrodysplasia ossificans progressiva * Fibrous dysplasia * Fong disease (or Nail–patella syndrome) * Fracture G * Giant cell tumor of bone * Greenstick fracture * Gout H * Hypophosphatasia * Hereditary multiple exostoses K * Klippel–Feil syndrome M * Metabolic bone disease * Multiple myeloma N * Nail–patella syndrome O * Osteitis * Osteitis deformans (or Paget's disease of bone) * O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paraneoplastic Syndrome
A paraneoplastic syndrome is a syndrome (a set of signs and symptoms) that is the consequence of a tumor in the body (usually a cancerous one), specifically due to the production of chemical signaling molecules (such as hormones or cytokines) by tumor cells or by an immune response against the tumor. Unlike a mass effect, it is not due to the local presence of cancer cells. Paraneoplastic syndromes are typical among middle-aged to older patients, and they most commonly present with cancers of the lung, breast, ovaries or lymphatic system (a lymphoma). Sometimes, the symptoms of paraneoplastic syndromes show before the diagnosis of a malignancy, which has been hypothesized to relate to the disease pathogenesis. In this paradigm, tumor cells express tissue-restricted antigens (e.g., neuronal proteins), triggering an anti-tumor immune response which may be partially or, rarely, completely effective in suppressing tumor growth and symptoms. Patients then come to clinical attention ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hyperparathyroidism
Hyperparathyroidism is an increase in parathyroid hormone (PTH) levels in the blood. This occurs from a disorder either within the parathyroid glands (primary hyperparathyroidism) or as response to external stimuli (secondary hyperparathyroidism). Symptoms of hyperparathyroidism are caused by inappropriately normal or elevated blood calcium leaving the bones and flowing into the blood stream in response to increased production of parathyroid hormone. In healthy people, when blood calcium levels are high, parathyroid hormone levels should be low. With long-standing hyperparathyroidism, the most common symptom is kidney stones. Other symptoms may include bone pain, weakness, depression, confusion, and increased urination. Both primary and secondary may result in osteoporosis (weakening of the bones). In 80% of cases, primary hyperparathyroidism is due to a single benign tumor known as a parathyroid adenoma. Most of the remainder are due to several of these adenomas. Very rarely it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypoparathyroidism
Hypoparathyroidism is decreased function of the parathyroid glands with underproduction of parathyroid hormone (PTH). This can lead to low levels of calcium in the blood, often causing cramping and twitching of muscles or tetany (involuntary muscle contraction), and several other symptoms. It is a very rare disease. The condition can be inherited, but it is also encountered after thyroid or parathyroid gland surgery, and it can be caused by immune system-related damage as well as a number of rarer causes. The diagnosis is made with blood tests, and other investigations such as genetic testing depending on the results. The primary treatment of hypoparathyroidism is calcium and vitamin D supplementation. Calcium replacement or vitamin D can ameliorate the symptoms but can increase the risk of kidney stones and chronic kidney disease. Additionally, injectable medications such as recombinant human parathyroid hormone or teriparatide may be given by injection to replace the missi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parathyroid Hormone 2 Receptor
Parathyroid hormone 2 receptor is a protein that in humans is encoded by the ''PTH2R'' gene. Function The protein encoded by this gene is a member of the G protein-coupled receptor family 2. This protein is a receptor for parathyroid hormone (PTH). This receptor is more selective in ligand recognition and has a more specific tissue distribution compared to parathyroid hormone 1 receptor (PTH1R). It is activated by PTH but not by parathyroid hormone-like hormone (PTHLH) and is particularly abundant in the brain and pancreas. The molecular interaction of the PTH2 receptor with the peptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. ... TIP39 has been characterized in full 3D molecular detail, identifying among other residues Tyr-318 in transmembrane helix 5 as a key residue fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parathyroid Hormone 1 Receptor
Parathyroid hormone/parathyroid hormone-related peptide receptor, also known as parathyroid hormone 1 receptor (PTH1R), is a protein that in humans is encoded by the ''PTH1R'' gene. PTH1R functions as a parathyroid hormone receptor, receptor for parathyroid hormone (parathyroid hormone, PTH) and for parathyroid hormone-related protein (Parathyroid hormone-related protein, PTHrP), also called parathyroid hormone-like hormone (PTHLH). Function This "classical" PTH receptor is expressed in high levels in bone and kidney and regulates calcium ion homeostasis through activation of adenylate cyclase and phospholipase C. In bone, it is expressed on the surface of osteoblasts. When the receptor is activated through PTH binding, osteoblasts express RANKL (Receptor Activator of Nuclear Factor kB Ligand), which binds to RANK (Receptor Activator of Nuclear Factor kB) on osteoclasts. This turns on osteoclasts to ultimately increase the resorption rate. Mechanism It is a member of the secretin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcitonin
Calcitonin is a 32 amino acid peptide hormone secreted by parafollicular cells (also known as C cells) of the thyroid (or endostyle) in humans and other chordates. in the ultimopharyngeal body. It acts to reduce blood calcium (Ca2+), opposing the effects of parathyroid hormone (PTH). Its importance in humans has not been as well established as its importance in other animals, as its function is usually not significant in the regulation of normal calcium homeostasis. It belongs to the calcitonin-like protein family. Historically calcitonin has also been called thyrocalcitonin. Biosynthesis and regulation Calcitonin is formed by the proteolytic cleavage of a larger prepropeptide, which is the product of the CALC1 gene (). It is functionally an antagonist with PTH and Vitamin D3. The CALC1 gene belongs to a superfamily of related protein hormone precursors including islet amyloid precursor protein, calcitonin gene-related peptide, and the precursor of adrenomedullin. Secretio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dalton (unit)
The dalton or unified atomic mass unit (symbols: Da or u) is a non-SI unit of mass widely used in physics and chemistry. It is defined as of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at rest. The atomic mass constant, denoted ''m''u, is defined identically, giving . This unit is commonly used in physics and chemistry to express the mass of atomic-scale objects, such as atoms, molecules, and elementary particles, both for discrete instances and multiple types of ensemble averages. For example, an atom of helium-4 has a mass of . This is an intrinsic property of the isotope and all helium-4 atoms have the same mass. Acetylsalicylic acid (aspirin), , has an average mass of approximately . However, there are no acetylsalicylic acid molecules with this mass. The two most common masses of individual acetylsalicylic acid molecules are , having the most common isotopes, and , in which one carbon is carbon-13. The molecular ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
