PARATHYROID FUNCTION IN PRIMARY OSTEOPOROSIS

Parathyroid hormone and 25-hydroxyvitamin D concentrations were measured in patients with severe primary osteoporosis and the results were compared with those found in normal subjects and in patients with primary hyperparathyroidism of vitamin D deficiency. The parathyroid hormone concentrations in 19 patients with primary osteoporosis were within the normal range, both in the basal state (215 ± 85 ng/l, mean ± SD) and during a maximal stimulation (460 ± 154 ng/l) induced by the infusion of disodium EDTA (70 mg/kg body weight). Increased serum concentrations of parathyroid hormone were found in patients with primary hyperparathyroidism (821 ± 323 ng/l, n = 33) and nutritional vitamin D deficiency (565 ± 144 ng/l, n = 11). Serum 25-hydroxy-vitamin D concentrations (16.8 ± 7.7 μg/l) were found to be normal in patients with primary osteoporosis. Slightly (9.1 ± 2.1 μg/l) or markedly lower (2.2 ± 1.1 μg/l) 25-hydroxy-vitamin D concentrations were found respectively in patients with primary hyperparathyroidism and secondary hyperparathyroidism due to vitamin D deficiency. The serum concentration of the vitamin D-binding protein was normal in all groups. A clearcut separation was therefore obtained between osteoporotic subjects (normal parathyroid hormone and normal 25-hydroxy-vitamin D concentrations) and patients with either primary hyperparathyroidism (increased parathyroid hormone and normal 25-hydroxy-vitamin D) or vitamin D deficiency (high parathyroid hormone and very low 25-hydroxy-vitamin D).