Hormone replacement therapy in postmenopausal women: endometrial hyperplasia and irregular bleeding

The decline in circulating oestrogen around the time of the menopause often induces unacceptable symptoms that affect the health and well being of women. Hormone replacement therapy (both unopposed oestrogen and oestrogen and progestogen combinations) is an effective treatment for these symptoms. In women with an intact uterus, unopposed oestrogen may induce endometrial stimulation and increase the risk of endometrial hyperplasia and carcinoma. The addition of progestogen reduces this risk but may cause unacceptable symptoms, bleeding and spotting which can affect adherence to therapy.

The objective of this review is to assess which hormone replacement therapy regimens provide effective protection against the development of endometrial hyperplasia and/or carcinoma with a low rate of abnormal vaginal bleeding.

Electronic searches for relevant randomised controlled trials of the Cochrane Menstrual Disorders and Subfertility Group Register of Trials, MEDLINE, EMBASE, PsychLIT, Current Contents, Biological Abstracts, Social Sciences Index and CINAHL were performed. Attempts were also made to identify trials from citation lists of review articles and drug companies were contacted for unpublished data. In most cases, the corresponding author of each included trial was contacted for additional information.

The inclusion criteria were randomised comparisons of unopposed oestrogen therapy, combined continuous oestrogen-progestogen therapy and sequential oestrogen-progestogen therapy with each other and placebo administered over a minimum treatment period of six months. Trials had to assess which regimen was the most protective against the development of endometrial hyperplasia/carcinoma and/or caused the lowest rate of irregular bleeding.

Twenty three RCTs were identified and five were excluded. The reviewers assessed the eighteen included studies for quality, extracted the data independently and odds ratios for dichotomous outcomes were estimated. Outcomes analysed included frequency of endometrial hyperplasia or carcinoma, frequency of irregular bleeding and unscheduled biopsies or dilation and curettage, and adherence to therapy.

Unopposed moderate or high dose oestrogen therapy was associated with a significant increase in rates of endometrial hyperplasia with increasing rates at longer duration of treatment and follow up. Odds ratios ranged from 5.4 (1. 4-20.9) for 6 months of treatment to 16.0 (9.3-27.5) for 36 months of treatment with moderate dose oestrogen (in the PEPI trial, 62% of those who took moderate dose oestrogen had some form of hyperplasia at 36 months compared to 2% of those who took placebo). Irregular bleeding and non adherence to treatment were also significantly more likely under these unopposed oestrogen regimens with greater effects with higher dose therapy. There was no evidence of increased hyperplasia rates, however, with low dose oestrogen. The addition of progestogens, either in continuous combined or sequential regimens, helped to prevent the development of endometrial hyperplasia and improved adherence to therapy (odds ratios of 3.7 for sequential therapy and 6.0 for continuous therapy). Irregular bleeding, however, was more likely under a continuous than a sequential oestrogen-progestogen regimen (OR = 2.3, 95% CI 2.1-2.5) but at longer duration of treatment, continuous therapy was more protective than sequential therapy in preventing endometrial hyperplasia (OR = 0.3, 95% CI 0.1-0.97). There was evidence of a higher incidence of hyperplasia under long cycle sequential therapy (progestogen given every 3 months) compared to monthly sequential therapy (progestogen given every month). No increase in endometrial cancer was seen in any of the treatment groups during the limited duration (maximum of 3 years) of these trials. (ABSTRACT TRUNCATED)