Acute effects of parathyroid hormone on vitamin D metabolism in patients with the bone loss of aging.

This study was carried out to evaluate the effects of an iv injection of parathyroid extract on serum levels of 1,25-dihydroxyvitamin D [1,25-(OH)2D3] in elderly osteopenic patients and age-matched nonosteopenic controls. Serum concentrations of 1,25-(OH)2D were reduced in elderly osteopenic subjects (mean +/- SEM, 20 +/- 3 pg/ml) compared with values in age-matched nonosteopenic controls (35 +/- 3 pg/ml), whereas no differences were found in serum 24,25-dihydroxyvitamin D levels (1.5 +/- 0.