Comparison of vitamin D metabolism in early healthy and late osteoporotic postmenopausal women.

We studied 20 healthy premenopausal women aged 36.5 +/- 4.0 years (mean +/- 1 SD), 123 healthy postmenopausal women aged 50.0 +/- 2.4 years, and 103 postmenopausal women aged 65.1 +/- 5.6 years with symptomatic osteoporosis (forearm and spinal fracture). Serum levels of vitamin D metabolites [25(OH)D, 24,25(OH)2D3, and 1,25-(OH)2D] were compared with (1) bone mass in the forearm (single photon absorptiometry) and in the spine (dual photon absorptiometry); (2) biochemical indices of bone formation (serum alkaline phosphatase, plasma bone Gla protein), and bone resorption (fasting urinary hydroxyproline); and (3) other biochemical estimates of calcium metabolism (serum calcium, serum phosphate, 24-hour urinary calcium, intestinal absorption of calcium). The present study revealed no difference in any of the vitamin D metabolites between the premenopausal women, the healthy postmenopausal women and the osteoporotic women as a group. The concentrations of 1,25(OH)2D and 25(OH)D were significantly lower in patients with spinal fracture than in those with forearm fracture. In the early postmenopausal women serum 1,25(OH)D was related to forearm bone mass (r = -0.20; P less than 0.05), intestinal calcium absorption (r = 0.18; P less than 0.05), and 24-hour urinary calcium (r = 0.21; P less than 0.05); serum 25(OH)D was related to spinal bone mass (r = 0.23; P less than 0.01). In the osteoporotic women, serum vitamin D metabolites were not related to bone mass, but 1,25(OH)2D was related to bone Gla protein (r = 0.33; P less than 0.001), serum phosphate (r = -0.27; P less than 0.01), and 24-hour urinary calcium (r = 0.43; P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)