A TEST OF 1,25‐DIHYDROXYVITAMIN D3 SECRETORY CAPACITY IN NORMAL SUBJECTS FOR APPLICATION IN METABOLIC BONE DISEASES

Abstract

The circulating concentration of 1,25‐dihydroxyvitamin D3 [1,25‐(OH)2D3] varies in man in response to a variety of physiological stimuli. In pathological states, random plasma 1,25‐(OH)2D3 levels reflect the sum of the underlying pathological process and the homeostatic corrections to those perturbations. Hence random 1,25‐(OH)2D3 levels do not allow differentiation as to whether changes in 1,25‐(OH)2D3 production or metabolism are primary or secondary to other changes. Similarly random levels do not provide much insight into the reserve of 1,25‐(OH)2D3 secretory capacity. We have developed a single infusion of parathyroid extract (PTE) as a test of 1,25‐(OH)2D3 secretory capacity. Normal re..