Prevention of postmenopausal bone loss by low and conventional doses of calcitriol or conjugated equine estrogen

Objectives: Estrogen deficiency is the most common cause of postmenopausal osteoporosis and estrogen replacement is well known to retard postmenopausal bone loss. Calcium supplement alone is generally considered to be insufficient for the prevention of bone loss associated with estrogen deficiency while the role of calcitriol is unclear. In the present study we examined the efficacy different doses of estrogen or calcitriol in the prevention of postmenopausal bone loss in Thais. Methods: The subjects consisted of 146 Thai women no more than 6 years postmenopausal. The subjects were randomly allocated to receive 750 mg supplemental calcium alone, calcium and conjugated equine estrogen (CEE) at 0.3 or 0.625 mg, calcium and calcitriol at 0.25 or 0.5 μg daily. Those receiving CEE also took 5 mg medrogestone for 12 days each month. BMD at L2-4 and femoral neck were measured at baseline 1 year and 2 years after treatments. Data were expressed as mean±S.E. Results: Subjects on supplemental calcium alone had approximately 2.5% decreases in L2-4 (P<0.05) and femoral BMD (P<0.01) at 2 years. CEE (0.3 mg) resulted in 3.20±1.2% increase in vertebral BMD (P<0.05) while no significant change in BMD was demonstrated at the femoral neck. Likewise, 0.625 mg of CEE induced 5.4±1.4% increase in vertebral BMD at 2 years (P<0.001) without change in the femoral BMD. In regard to calcitriol, no significant change in vertebral or femoral BMD was demonstrated with either 0.25 or 0.5 μg calcitriol. Conclusion: We concluded that calcitriol is effective in the prevention of early postmenopausal bone loss in Thais. It represents an option for the prevention of osteoporosis in postmenopausal women who are contraindicated for estrogen replacement.