Low 1,25-dihydroxyvitamin D, secondary hyperparathyroidism, and normal osteocalcin in elderly subjects.

The relationship among serum vitamin D metabolites, PTH, and osteocalcin concentrations was investigated in 20 elderly subjects. All except 2 had subnormal 25-hydroxyvitamin D concentrations. Eighteen (90%) had subnormal serum 1,25-dihydroxyvitamin D [1,25-(OH)2D] concentrations, while 8 subjects (40%) had elevated PTH concentrations. There was a highly significant inverse relationship between PTH and 1,25-(OH)2D concentrations. Serum osteocalcin concentrations were not elevated in any subject, and in fact, the mean osteocalcin concentration was in the lower part of the normal range. These data indicate no compensatory increase in 1,25-(OH)2D in response to secondary hyperparathyroidism and no increase in osteocalcin in response to hypersecretion of PTH in the elderly. These 2 defects may contribute to the bone disease of the elderly.