parathyroid glands


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Related to parathyroid glands: Adrenal glands, parathyroid hormone, pancreas, hyperparathyroidism

parathyroid

 [par″ah-thi´roid]
1. near the thyroid 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 glands

Four, 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 glands

small 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.
Table 1: Hormones
Site of productionName of hormoneMain targetsInvolved in regulating:Secretion controlled by:
HypothalamusReleasing and inhibiting hormonesAnterior pituitary (via local blood vessels)Secretion of anterior pituitary hormonesOther brain regions; feedback re regulated hormones and their actions
Neurohormones released from posterior pituitary:
OxytocinUterus, breastsLabour and lactationAfferent information from target organs
Antidiuretic hormone (ADH, vasopressin)KidneysWater loss: ECF volume and osmolalityHypothalamic osmoreceptors
Anterior pituitary(Human) growth hormone (H)GHMost cellsGrowth and metabolismHypothalamic releasing and inhibiting hormones via local blood vessels
ProlactinBreastsMilk production
Trophic hormones:
Thyroid-stimulating (TSH)Thyroid glandThyroid secretions
GonadotrophinsOvary or testisGerm cell maturation and hormone secretions
Adrenocorticotrophic (ACTH)Adrenal cortexCortisol secretion
Pineal bodyMelatoninWidespread, including brain, thymus, etc.
  • Sleep/wake cycle
  • Antioxidant
  • Immune system
Hypothalamus; varying light input from retina
Thyroid
  • Thyroxine
  • Triiodothyronine
  • Calcitonin
  • Most cells
  • Bone, kidneys, gut
  • Cellular oxidative metabolism
  • Decreases ECF [Ca2+]
  • TSH from anterior pituitary. Negative feedback from blood hormone concentration
  • ECF [Ca2+]
ParathyroidsParathormoneBone, kidneys, gut
  • Calcium and phosphorus absorption, secretion and turnover in bone.
  • Increases ECF [Ca2+]
ECF [Ca2+]
Adrenal: Cortex
  • Cortisol
  • Aldosterone
  • Androgens
  • Most cells
  • Kidneys
  • Gonads & other tissues
  • Metabolism
  • Response to stress
  • Na and K balance
  • Sex characteristics and reproductive function
  • ACTH from anterior pituitary
  • ECF [Na+] [K+]
  • Renin-angiotensin
  • ACTH
Medulla
  • Adrenaline
  • Noradrenaline
Heart, smooth muscle, glandsCardiovascular and metabolic adjustments to activity and stressSympathetic nervous system
Atrial wallAtrial natriuretic hormoneKidneysBlood volume; increases sodium (therefore also water) loss in urineStretch of atrial wall by venous pressure
Gonads: TestisAndrogens (mainly testosterone)Genitalia and other tissuesReproductive function and sex characteristicsAnterior pituitary gonadotrophins
Ovary
  • Oestrogens
  • Progesterone
Uterus, breasts and other tissuesMenstrual cycle, pregnancy, lactation
Pancreas
  • Insulin, glucagon
  • Somatostatin
  • Most cells
  • Other secretory cells in the pancreas
Blood levels, storage and cellular uptake of nutrients, notably glucose, but also proteins and fatsBlood levels of nutrients; autonomic nervous system; other gastrointesinal hormones
Alimentary tract
StomachGastrinGastric acid-secreting cellsGastrointestinal functions: motility, digestive juices and other secretionsLocal chemical and mechanical factors in the alimentary tract
Small intestine
  • Secretin
  • Cholecystokinin- pancreozymin (CCK-PZ)
  • Somatostatin, motilin
  • Other peptide hormones including vasoactive intestinal peptide (VIP)
  • Widespread on
  • GI tract
Several GI functions including bile flow, pancreatic enzyme and exocrine secretionsIngestion of food, distension of GI tract
References in periodicals archive ?
Etelcalcetide binds to and activates the calcium-sensing receptor on the parathyroid gland, thereby decreasing PTH levels.
2) The most common cause of primary hyperparathyroidism is an adenoma in a single parathyroid gland (75 to 85% of cases).
One hypothesis postulates that African grey parrots, secondary to viral damage to the parathyroid gland, lack the ability to mobilize skeletal calcium in response to hypocalcemia.
Up to 50% of neonates experience postpartum hypocalcemia secondary to elevated maternal calcium levels that suppress the fetal parathyroid glands (1, 3).
4) Rare reports of the presence of 7 and up to 12 parathyroid glands have been described in the literature.
It uses a small incision under the arm to remove all or a portion of the thyroid or parathyroid glands without leaving a scar on the neck.
Aspiration of enlarged parathyroid glands for parathyroid hormone assay.
Parathyroid imaging has no role in the diagnosis of PHPT but is usually done to help the surgeon in identifying the anatomic localization of abnormally functioning or enlarged parathyroid glands (3).
Q I HAD an operation on my thyroid gland to remove a swelling and was told later my parathyroid glands had been damaged and I would need to take medicine for the rest of my life.
Parathyroid glands are usually four in number, each measuring 5 mm in diameter.
Parathyroid hormone (PTH) is synthesized by four parathyroid glands which are located close to or on the posterior surface of the thyroid gland.
Older adults with low blood levels of vitamin D and high blood levels of a hormone secreted by the parathyroid glands, which regulate calcium, may have a higher risk of depression, according to a report in the May issue of Archives of General Psychiatry.

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