A systematic review including 11 studies with a total of 2218 postmenopausal women (mean age from 47 to 72 years) was abstracted in DARE. Several cyclic and continuous regimens of oestrogens (conjugated equine oestrogen, estradiol, mestranol) and progestins (medroxyprogesterone acetate, norethindrone acetate, micronised progesterone) were used in the included studies. The duration of active treatment varied from 1 to 5 years and the follow-up after treatment discontinuation from 1 to 4 years. After stopping hormone therapy (HT), the mean spinal bone loss ranged from 2.3% to 6.2% in the first year (9 studies). Increases in bone turnover markers also occurred rapidly when hormone therapy was stopped. Mean age, enrolment for prevention or treatment of osteoporosis (different bone mineral density (BMD) levels) and duration of prior treatment had no obvious effect on the magnitude of bone loss. Women in the placebo groups who had not received HT experienced changes in BMD, ranging from -1.9% to 0.1% per year in the 'discontinuation' phase and from -0.6% to -1.8% during the 'active' (randomised to placebo) treatment phase. At completion of follow-up after stopping HT, the mean BMD was not significantly higher than baseline in most studies. In no study did stopping HT lead to a final mean BMD that was significantly lower than the untreated placebo group.
Comment: The quality of evidence is downgraded by limitations in the review quality and by heterogeneity between studies.