Which organ secretes pth

Internally, the gland consists of follicles, which produce thyroxine and triiodothyronine hormones. These hormones contain iodine. About 95 percent of the active thyroid hormone is thyroxine, and most of the remaining 5 percent is triiodothyronine. Both of these require iodine for their synthesis. Thyroid hormone secretion is regulated by a negative feedback mechanism that involves the amount of circulating hormone , hypothalamus , and adenohypophysis.

If there is an iodine deficiency , the thyroid cannot make sufficient hormone. This stimulates the anterior pituitary to secrete thyroid-stimulating hormone , which causes the thyroid gland to increase in size in a vain attempt to produce more hormones. Further information on the symptoms for each condition can be found in the individual articles. Too little parathyroid hormone or hypoparathyroidism , is a rare medical condition.

It can result in low levels of calcium in the blood hypocalcaemia. It is usually treated medically with oral calcium and vitamin D analogues but the availability of parathyroid hormone replacement therapy may change the approach to treatment for some patients. About Contact Events News.

Search Search. You and Your Hormones. Students Teachers Patients Browse. Human body. Home Hormones Parathyroid hormone. Parathyroid hormone accomplishes its job by stimulating at least three processes:.

Addition information on how parathyroid hormone and vitamin D control calcium balance can be found in the section Endocrine Control of Calcium Homeostasis. Parathyroid hormone is released in response to low extracellular concentrations of free calcium.

Changes in blood phosphate concentration can be associated with changes in parathyroid hormone secretion, but this appears to be an indirect effect and phosphate per se is not a significant regulator of this hormone. When calcium concentrations fall below the normal range, there is a steep increase in secretion of parathyroid hormone. Low levels of the hormone are secreted even when blood calcium levels are high.

The figure to the right depicts parathyroid hormone release from cells cultured in vitro in differing concentrations of calcium. The parathyroid cell monitors extracellular free calcium concentration via an integral membrane protein that functions as a calcium-sensing receptor.