Abstract: Twenty studies with 1969 women were included in this review. These studies compared GnRHa, danazol and progestogens versus placebo or no treatment; GnRHa versus danazol, progestogens, GnRH antagonists or dilatation & curettage; and danazol versus progestogens. Four studies performed more than one comparison. When compared with no treatment, GnRHa used before hysteroscopic resection were associated with a higher rate of postoperative amenorrhoea at 12 months (RR 1.6, 95% CI 1.2 to 2.0, 7 RCTs, 605 women, moderate heterogeneity; I2 = 40%) and at 24 months (RR 1.62, 95% CI 1.04 to 2.52, 2 RCTs, 357 women, no heterogeneity; I2 = 0%), a slightly shorter duration of surgery (-3.5 minutes, 95% CI -4.7 to -2.3, 5 RCTs, 156 women, substantial heterogeneity; I2 = 72%) and greater ease of surgery (RR 0.32, 95% CI 0.22 to 0.46, 2 RCTs, 415 women, low heterogeneity; I2 = 4%). Postoperative dysmenorrhoea was reduced (RR 0.59, 95% CI 0.40 to 0.87, 2 RCTs, 133 women, no heterogeneity; I2 = 0%). The use of GnRHa had no effect on intraoperative complication rates (RR 1.47, 95% CI 0.35 to 6.06, 5 RCTs, 592 women, no heterogeneity; I2 = 0%), and participant satisfaction with this surgery was high irrespective of the use of pre-operative endometrial thinning agents (RR 0.99, 95% CI 0.93 to 1.05, 6 RCTs, 599 women, low heterogeneity; I2 = 11%). GnRHa produced more consistent endometrial atrophy than was produced by danazol (RR 1.84, 95% CI 1.23 to 2.75, 2 RCTs, 142 women, no heterogeneity; I2 = 0%). For other intraoperative and postoperative outcomes, any differences were minimal, and no benefits of GnRHa pretreatment were noted in studies in which women underwent second-generation ablation techniques. Both GnRHa and danazol produced side effects in a significant proportion of women, although few studies reported these in detail. Few randomised data were available to allow assessment of the effectiveness of progestogens as endometrial thinning agents. When reported, the long-term effects of endometrial thinning agents on benefits such as postoperative amenorrhoea were reduced with time. The main study weaknesses were that most participants received no follow-up beyond 24 months and that the studies used a small sample size. Heterogeneity for outcomes reported ranged from none to substantial. More than half the trials had no blinding of participants or outcome assessment. Most of the trials were determined to have uncertain selection and reporting bias, as they did not report allocation concealment and evidence of selective reporting was noted. The quality of reporting of adverse events was generally poor, but, when described in the studies, they included menopausal symptoms such as hot flushes, vaginal dryness, hirsutism, decreased libido and voice changes, as well as other side effects such as headache and weight gain. Low-quality evidence suggests that endometrial thinning with GnRHa and danazol before hysteroscopic surgery improves operating conditions and short-term postoperative outcomes. GnRHa produced slightly more consistent endometrial thinning than was produced by danazol, although both achieved satisfactory results. The effect of these agents on longer-term postoperative outcomes was reduced with time. No benefits of GnRHa pretreatment were apparent with second-generation ablation techniques. Also, side effects were more common when these agents were used.

Plain-language summary: The evidence is current to April 2013. The review included 20 randomised controlled trials with a total of 1969 premenopausal women with heavy menstrual bleeding for whom non-surgical treatment had not worked. Studies compared GnRH analogues, danazol and progestogens versus placebo or no treatment; GnRH analogues versus danazol, progestogens, GnRH antagonists or dilatation & curettage; and danazol versus progestogens. Four studies performed more than one comparison. Three studies used the newer second-generation surgical techniques for endometrial destruction. GnRH analogues and danazol used before hysteroscopic surgery improve both operating conditions for the surgeon and short-term bleeding symptoms for women (up to 24 months after surgery). GnRH analogues thin the lining of the womb better and more consistently than danazol, although both agents produce satisfactory results. Adverse effects were more common in women taking GnRH analogues or danazol compared with no treatment, and this was especially true with danazol. Adverse effects included menopausal symptoms such as hot flushes, vaginal dryness, hirsutism, decreased libido and voice changes, as well as other side effects such as headache and weight gain. The use of medications to thin the lining of the womb before surgery does not appear to improve heavy menstrual bleeding in the long term (i.e. longer than 24 months). However, only a few small studies followed up with women for longer than 24 months. Also, medications given to thin the womb lining do not provide additional benefit when used with the newer second-generation endometrial destruction techniques, which are being performed increasingly in hospitals. Overall, the quality of the evidence was very low because of risk of bias in the included studies and differences between the studies. The quality of reporting of adverse events was generally poor.