Box 5.5Overview of the hormonal control of calcium and phosphate homeostasis by parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D (1,25-(OH)2D)

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PTH stimulates the release of Ca2+ from bone by increasing osteolysis and resorption, increases Ca2+ reabsorption and phosphate excretion in the kidney and increases the conversion of inactive 25 hydroyxvitamin D (25-(OH)D) to the active 1,25-(OH)2D. Its secretion is stimulated by a reduction in plasma Ca2+ concentration. The main action of the active vitamin D, 1,25-(OH)2D, is to increase Ca2+ absorption in the gut and synergize with PTH on bone. Its production is increased by a reduction in circulating phosphate and increased PTH concentrations.

From: Chapter 5, The parathyroid glands and vitamin D

Cover of Endocrinology
Endocrinology: An Integrated Approach.
Nussey S, Whitehead S.
Copyright © 2001, BIOS Scientific Publishers Limited.

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