Thiazide for the postponement of postmenopausal bone loss

Abstract

The effect of thiazide on bone mineral loss in normal postmenopausal women was examined during a 3 yr placebocontrolled clinical trial. Sixty-three healthy women in their early menopause were randomized to treatment with bendroflumethiazide 5 mg/day or placebo for 2 yr, while both groups received placebo for the third year of the trial. Calcium supplement 0.5 g/day was given throughout the 36 mo to all participants. Bone mineral content (BMC) determined by 125I-photon absorptiometry of the forearms decreased 2% per year in the placebo group ( p < 0.001). In the thiazide group no fall in BMC was seen during the first 6 mo, whereafter BMC declined with the same rate as in the placebo group. At the end of the 3 yr trial BMC averaged 94.1% in the placebo group and 95.2% in the thiazide group ( p > 0.05). Despite a daily supplement of 0.5 g calcium, thiazide induced a persistent fall in the urinary calcium excretion of 25% ( p < 0.001), whereas the calcium supplement in the placebo group caused a significant increase in mean urine calcium of 10%–20% ( p < .001). At stop of thiazide medication a rebound effect caused a marked rise in urine calcium. One month after withdrawal of the calcium supplement the urinary calcium excretion had returned to the initial level in both groups. It is concluded that despite a sustained urine calcium lowering action the effect of thiazide upon postmenopausal bone loss is shortlived.