parathyroid gland


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Parathyroid gland

An endocrine organ usually associated with the thyroid gland and possessed by all vertebrates except the fishes. In response to lowered serum calcium concentration, a hormone is produced which promotes bone destruction and inhibits the phosphorus-conserving activity of the kidneys. See Thyroid gland

Common positions of human parathyroid glands on the posterior aspect of the thyroidenlarge picture
Common positions of human parathyroid glands on the posterior aspect of the thyroid

In humans, there are typically four glands situated as shown in the illustration; however, the number varies between three and six, with four appearing about 80% of the time. Variations in the positioning of the glands along the craniocaudal axis occur but, excepting parathyroid III which may occasionally be found upon the anterior surface of the trachea, the relation to the posterior surface of the thyroid is rarely lost.

The parathyroid glands are essential for the regulation of calcium and phosphate concentrations in the extracellular fluids of amphibians and higher vertebrates. Parathyroid hormone has two major target organs, bone and kidney. It acts on bone in several ways. Short-term changes include a rapid uptake of bone fluid calcium into osteoblast cells, which in turn pump the calcium into the extracellular fluids. Long-term effects include increased activity and number of osteoclasts, bone cells which act to break down bone matrix and release calcium from bone. All of these effects result in increased blood calcium values. See Bone, Calcium metabolism

Parathyroid hormone inhibits the renal reabsorption of phosphate, thus increasing the urinary output of phosphate. Phosphate reabsorption across the renal tubule is dependent upon sodium transport, and parathyroid hormone interferes with this sodium-dependent phosphate transport in the proximal tubule. Another important effect of parathyroid hormone on the kidney is to increase the renal reabsorption of calcium, thus reducing the loss of calcium in the urine and conserving calcium in the body. See Kidney

Finally, there are reports that parathyroid hormone indirectly stimulates calcium uptake into the body across the intestine. Parathyroid hormone stimulates the production of the most active metabolite of vitamin D, 1,25-dihydroxycholecalciferol, during vitamin D synthesis. This metabolite of vitamin D directly stimulates the intestinal absorption of calcium. See Endocrine system (vertebrate), Parathyroid hormone

parathyroid gland

[¦par·ə′thī‚rȯid ‚gland]
(anatomy)
A paired endocrine organ located within, on, or near the thyroid gland in the neck region of all vertebrates except fishes.
References in periodicals archive ?
However, the use of a low-frequency transducer, such as a 5 MHz, may not have the resolution to detect a small (<1 cm) hyperplastic parathyroid gland at depth.
During the MIP, which was directed towards the right lower parathyroid gland as indicated by sestamibi scanning, an abnormal parathyroid gland was found and removed.
The main regulatory gene in development of parathyroid gland is GCMB.
Probably, when SLN was tracked by nano-carbon, lymph nodes were black, and parathyroid gland was not stained; but when SLN was tracked by methylene blue, both lymph nodes and parathyroid were stained blue, which could hardly be identified.
Compared to chief cells in normal parathyroid glands, the chief cells in adenomas may have enlarged pleomorphic nuclei and cytoplasm that contains minimal amounts of lipids.
The fallen one: The inferior parathyroid gland that descends into the mediastinum.
Adenoma causes the parathyroid glands to secrete more parathyroid hormone, which is called primary hyperparathyroidism.
This method minimizes the surgical damage to both the parathyroid glands and the RLN.
Health Briefs TV covers everything you want to know about parathyroid gland function.
Acute parathyroid insufficiency is considered as the main factor affecting postoperative calcium levels and occurs due to incidental parathyroidectomy (IPT), parathyroid gland (PG) injury, or devascularization [3].
Radionuclide parathyroid imaging using technetium sestamibi scan revealed slow washout in the right mid thyroid region (Figure 3) and computed tomography (CT) scan of the neck without contrast revealed a soft tissue mass posterior to mid pole of the right thyroid lobe (Figure 4) both favoring a diagnosis of adenoma of the right inferior parathyroid gland.
An enlarged parathyroid gland was recognized as a homogeneously echogenic structure with less echogenicity than the thyroid gland.