Chemistry and physiology of parathyroid hormone.

Many recent studies, only a few of which are reviewed here (see Habener & Potts, 1976, for a detailed summary) have led to considerable clarification concerning critical features of the chemistry, biosynthesis, secretion and mode of action of parathyroid hormone. Certain of the confusion recently experienced in measurements of parathyroid hormone in blood is clearly explained by the heterogeneity arising from various forms of parathyroid hormone arising during biosynthesis and metabolism. Ultimately, as critical features of biosynthesis and metabolism of PTH as well as chemical definition of various molecular forms are achieved, considerable refinement in immunoassays should result. These advances in turn should provide better insights into the role of parathyroid dysfunction in various disorders of calcium and skeletal metabolism. From the physiological viewpoint, a clearer appreciation of the homeostatic role of parathyroid hormone in calcium metabolism is emerging as the essential features of biosynthesis, release, metabolism and action of the hormone are uncovered.