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1. near the thyroid gland.
2. a parathyroid gland.
3. a preparation containing parathyroid hormone from animal parathyroid glands; used for diagnosis and treatment of hypoparathyroidism.
parathyroid glands four small endocrine bodies in the region of the thyroid gland; they contain two types of cells: chief cells and oxyphils. Chief cells are the major source of parathyroid hormone (PTH), the secretion of which is dependent on the serum calcium level. Through a closed-loop feedback mechanism a low serum calcium level stimulates secretion of PTH; conversely, a high serum calcium level inhibits its secretion. The essential role of PTH is maintenance of a normal serum calcium level in association with vitamin D and calcitonin. It does this by exerting its effects on bone, kidney, and gastrointestinal tract. In bone, it enhances bone resorption by increasing digestion of the bone matrix by osteoclasts, which produces calcium that gets released into the bloodstream. In the kidney, PTH increases the excretion of phosphate and the reabsorption of filtered calcium. In the intestine, it increases intestinal absorption of calcium. The parathyroid glands may be subject to either hyperparathyroidism or hypoparathyroidism.
parathyroid glandsFour, yellow, bean-shaped bodies, each about 0.5 cm long, lying behind the THYROID GLAND, usually embedded in its capsule. The parathyroids secrete a hormone, parathyroid hormone (parathormone or PTH), into the blood if the level of calcium in the blood drops. This hormone promotes the release of calcium from the bones, controls loss in the urine and increases absorption from the intestine, thus correcting the deficiency in the blood. Maintenance of accurate levels of blood calcium is more important, physiologically, than the strength of the bones. Secretion of abnormal quantities of PTH from a parathyroid tumour can lead to bone softening. Underaction of the parathyroids causes a dangerous drop in the blood calcium.
Sandström,Ivor V., swedish anatomist, 1852-1889.
Sandström bodies - Synonym(s): parathyroid glands
parathyroid glandssmall clumps of endocrine tissue (usually four) on the back of the thyroid gland which secrete parathyroid homone (PTH). This acts to increase calcium ion concentration in the extracellular fluid, counterbalanced by calcitonin from the thyroid gland which has the opposite effects. Together they correct any changes in blood [Ca2+] by action on absorption of calcium from the gut, its deposition in bone and its excretion by the kidneys. See also hormones; Table 1.
|Site of production||Name of hormone||Main targets||Involved in regulating:||Secretion controlled by:|
|Hypothalamus||Releasing and inhibiting hormones||Anterior pituitary (via local blood vessels)||Secretion of anterior pituitary hormones||Other brain regions; feedback re regulated hormones and their actions|
|Neurohormones released from posterior pituitary:|
|Oxytocin||Uterus, breasts||Labour and lactation||Afferent information from target organs|
|Antidiuretic hormone (ADH, vasopressin)||Kidneys||Water loss: ECF volume and osmolality||Hypothalamic osmoreceptors|
|Anterior pituitary||(Human) growth hormone (H)GH||Most cells||Growth and metabolism||Hypothalamic releasing and inhibiting hormones via local blood vessels|
|Thyroid-stimulating (TSH)||Thyroid gland||Thyroid secretions|
|Gonadotrophins||Ovary or testis||Germ cell maturation and hormone secretions|
|Adrenocorticotrophic (ACTH)||Adrenal cortex||Cortisol secretion|
|Pineal body||Melatonin||Widespread, including brain, thymus, etc.||Hypothalamus; varying light input from retina|
|Parathyroids||Parathormone||Bone, kidneys, gut||ECF [Ca2+]|
|Medulla||Heart, smooth muscle, glands||Cardiovascular and metabolic adjustments to activity and stress||Sympathetic nervous system|
|Atrial wall||Atrial natriuretic hormone||Kidneys||Blood volume; increases sodium (therefore also water) loss in urine||Stretch of atrial wall by venous pressure|
|Gonads: Testis||Androgens (mainly testosterone)||Genitalia and other tissues||Reproductive function and sex characteristics||Anterior pituitary gonadotrophins|
|Ovary||Uterus, breasts and other tissues||Menstrual cycle, pregnancy, lactation|
|Pancreas||Blood levels, storage and cellular uptake of nutrients, notably glucose, but also proteins and fats||Blood levels of nutrients; autonomic nervous system; other gastrointesinal hormones|
|Stomach||Gastrin||Gastric acid-secreting cells||Gastrointestinal functions: motility, digestive juices and other secretions||Local chemical and mechanical factors in the alimentary tract|
|Small intestine||Several GI functions including bile flow, pancreatic enzyme and exocrine secretions||Ingestion of food, distension of GI tract|