title: 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 responses in twelve males and six females consisted of an increase in plasma 1,25-(OH)2D3 levels of 78% over basal in the male and 77% over basal in the female subjects. The peak response occurred 18-22 h after the PTE was administered. This test of 1,25-(OH)2D3 secretory capacity should prove useful in the evaluation of patients with metabolic bone disease. As part of this study, the diurnal plasma 1,25-(OH)2D3 level was examined in six males and seven females. There was no significant diurnal rhythm between 8.00 and 22.00 h.
mesh_terms: D000328:Adult; D001851:Bone Diseases, Metabolic / Q000175:diagnosis*; D002117:Calcitriol / Q000097:blood / Q000378:metabolism*; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D008297:Male; D010281:Parathyroid Hormone; D012737:Sex Factors; D013997:Time Factors
chemical_list: D010281:Parathyroid Hormone; D002117:Calcitriol