Parathyroid hormone stimulates cells in what
Parathyroid hormone is the most important endocrine regulator of calcium and phosphorus concentration in extracellular fluid. This hormone is secreted from cells of the parathyroid glands and finds its major target cells in bone and kidney. This hormone is secreted from cells of the parathyroid glands and finds its major target cells in bone and kidney. Another hormone, parathyroid hormone-related protein, binds to the same receptor as parathyroid hormone and has major effects on development. 1 Suppression of calcium loss in urine: In addition to stimulating fluxes of calcium into blood from bone and intestine, parathyroid hormone puts a brake on excretion of calcium in urine, thus conserving calcium in blood. 2  This effect is mediated by stimulating tubular reabsorption of calcium. 1 Parathyroid hormone stimulates this process, but indirectly by stimulating production of the active form of vitamin D in the kidney. 2  Vitamin D induces synthesis of a calcium-binding protein in intestinal epithelial cells that facilitates efficient absorption of calcium into blood. When parathyroid hormone (PTH) binds to receptors on these cells, the osteocytic membrane pumps calcium ions from the bone fluid into the extracellular fluid. The slow phase of bone resorption occurs over several days and has 2 components. When calcium levels decrease, this stimulates the parathyroid gland to release parathyroid hormone. Parathyroid hormone encourages the normal process of bone breakdown (essential for maintenance and growth of the bone). This process of bone breakdown releases calcium into the bloodstream. hormone. a chemical transmitter substance produced by cells of the body and transported by the bloodstream to the cells and organs on which it has a specific regulatory effect. adj., adj hormo´nal. Hormones act as chemical messengers to body organs, stimulating certain life processes and retarding others. Parathyroid hormone (PTH) is a polypeptide containing 84 amino acids that is secreted by the parathyroid glands after cleavage from preproparathyroid hormone (115 amino acids) to proparathyroid hormone (90 amino acids) to the mature 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. Feedback inhibition of parathyroid hormone (PTH) release occurs primarily by direct effect of calcium at the level of the parathyroid gland. Although not well elucidated, 1,25-(OH) 2 D3 appears to exert a mild inhibitory effect on the parathyroid gland as well.
Parathyroid gland.