Deficient calcitonin response to calcium stimulation in postmenopausal osteoporosis?

To test whether mobilisation of immunoreactive calcitonin in response to calcium challenge is reduced in postmenopausal osteoporosis, seventeen postmenopausal osteoporotic women with compression fractures and ten normal age-matched women were given intravenous infusions of 3 mg/kg elemental calcium over a 10 min period. Blood samples were obtained 5 min before and at 0, 10, 20, and 60 min after start of infusion for the measurement of serum calcium and plasma immunoreactive calcitonin. Serum calcium increased significantly from baseline in both normal and osteoporotic groups; immunoreactive calcitonin increased significantly in the controls 10 min and 20 min after the start of infusion, but in the women with osteoporosis calcitonin levels did not change significantly at any time. 20 min after the start of infusion the change in immunoreactive calcitonin from baseline was significantly less in osteoporotic women than in the controls. These data are consistent with a decreased immunoreactive calcitonin response to calcium infusion in postmenopausal osteoporotic women, and suggest that calcitonin deficiency may be involved in the development of postmenopausal osteoporosis.