1,25-dihydroxycholecalciferol in hypophosphataemic osteomalacia presenting in adults.

The effects of exogenous 1,25-dihydroxycholecalciferol (1,25(OH)2D3) in two adults with late-onset hypophosphataemic osteomalacia were studied. In the presence of elevated 25-hydroxyvitamin D levels 1,25OH)2D3 improved intestinal 47Ca absorption and increased urinary calcium, phosphate and hydroxyproline excretion. Hypophosphataemia, parathyroid hormone and bone mineralization were not significantly affected. The rise of the 1,25-dihyroxyvitamin D concentrations was dose dependent. The results indicate htat the impared renal phosphate conservation--the primary defect in this disorder--is not corrected by exogneous 1,25-dihydroxycholecalciferol.