parathyroid glands


Also found in: Dictionary, Thesaurus, Encyclopedia.

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 ?
Parathyroid glands of at least 1 cm display vascularity by colour Doppler or power Doppler characterised by low resistance waveforms on spectral analysis.
Although inexpensive and readily available, monitoring the intraoperative ionized Ca and total Ca is not clinically reliable for confirming removal of hyperfunctioning parathyroid glands.
Superior parathyroid glands tend to be found dorsal to the mid-to-superior thyroid pole and in the retropharyngeal space (Figure 2).
Meanwhile, nuclear imaging has helped doctors pinpoint which parathyroid gland is diseased, reducing the need for exploratory surgery.
The first is primary hyperparathyroidism, which is the result of the hypersecretion of PTH by abnormal parathyroid glands, is relatively common, with an overall incidence of approximately 1 in 1,000.
In FMEN1, all four parathyroid glands tend to be overactive.
Your doctor can do a blood test to find out if your parathyroid glands are too active.
Primary hyperparathyroidism (PHPT) occurs as a result of unregulated over-production of parathyroid hormone (PTH) secreted from the parathyroid glands, leading to an inappropriate calcium homeostasis.
Hypoparathyroidism, designated an orphan disease by the European Commission (EC), is a rare disease that occurs when inadequate levels of PTH are secreted by the parathyroid glands.
Application of carbon nanoparticles suspensions injection can stain the lymph nodes of the center compartment while leaving the parathyroid glands unstained (because of the negative development of parathyroid glands to carbon nanoparticles, Chongqing Lummy Pharmaceuticals, China), thus helping to identify and protect parathyroid glands and the RLN [Figure 3] and [Figure 4], as well as facilitating the identification and clearance of lymph nodes.
The left recurrent laryngeal nerve and the parathyroid glands were identified, and dissection was extended through the ligament of Berry across the front face of the trachea and partway down the right side.
The cause of hypoparathyroidism in thalassemia is assumed to be iron deposition in parathyroid glands, but the reason why some patients develop hypoparathyroidism and others do not is not exactly known.

Full browser ?