CHANGES IN BONE-DENSITY IN WOMEN STARTING HORMONE REPLACEMENT THERAPYCOMPARED WITH THOSE IN WOMEN ALREADY ESTABLISHED ON HORMONE REPLACEMENT THERAPY

It is well established that hormone replacement therapy (HRT) will pre vent postmenopausal loss of bone. However, it is not known to what ext ent HRT will continue to affect bone mineral density (BMD) in women es tablished on HRT compared with those commencing treatment. We recruite d 48 healthy early postmenopausal women into a prospective, comparativ e study. Twenty-nine women had never taken HRT (group A) whilst 19 wom en were already taking HRT (group B) (conjugated equine oestrogens, 0. 625 mg daily; mean (+/-SD) years of use 2.2 (1.5) years). All of the w omen were started on, or switched to, micronized 17 beta-oestradiol (2 mg/day) continuously with dydrogesterone (10 mg/day) for the first 14 days of each cycle. BMD measurements were performed at the lumbar spi ne and proximal femur using dual-energy X-ray absorptiometry (DXA) at baseline and after 12 and 24 months of treatment. Group A showed a sig nificantly greater increase in lumbar spine BMD after 12, months (mean (+/-SD) = 5.3 (4.6)%) compared with group B (mean(+/-SD) = 2.1 (2.1)% ) and 24 months of treatment (group A, mean(+/-SD) = 6.4 (5.2)%; group B, mean (+/-SD) = 2.3 (2.6)%; both p <0.01). Femoral neck and Ward's triangle BMD increased significantly in both groups but there were no significant differences between the groups. Baseline BMD correlated wi th change in lumbar spine BMD for women in group A after 12 months (r = -0.67, p <0.01) and 24 months of treatment (r = -0.59, p <0.05). The se data demonstrate that HRT has the greatest effect on BMD when it is first administered, especially in those women with low BMD, but impro vements may still be observed in women continuing HRT in the longer te rm.