Parathyroid hormone and 1,25(OH)2D3 in chronic renal failure

Abstract

A number of different factors may affect the development of secondary hyperparathyroidism in chronic renal failure, but the most important ones regulating PTH secretion seem to be serum ionized calcium and levels of 1,25(OH)2D3. Whether these are indeed separate mechanisms or whether they are linked has yet to be determined. While low calcium increases PTH secretion, it does not increase PTH synthesis in vitro compared with normal. High calcium, on the other hand, suppresses PTH synthesis. Studies in patients and animals have shown that an increase or decrease in serum PTH levels can be achieved by maneuvers that alter either calcium or activated 1,25(OH)2D3 without changing the other.