Expression of sex steroid receptors and Ki-67 in the endometria of menorrhagic women: effects of intrauterine levonorgestrel.

The levonorgestrel-releasing intrauterine system (LNG-IUS) has proven to be the most effective medical treatment in reducing the amount of menstrual blood loss. However, the molecular mechanisms underlying menorrhagia and/or accounting for the therapeutic effect of the LNG-IUS are still obscure. In this study, we used immunohistochemistry to compare the distribution of sex steroid receptors and the proliferation marker Ki-67 in the endometria of women with and without menorrhagia before and after 6 and 12 months of treatment with an LNG-IUS. The study sample included 67 women (aged 35-49 years) who had spontaneous ovulatory cycles. In women with menorrhagia, secretory phase endometrium exhibited more proliferative activity than in women without menorrhagia. No significant differences were found in the immunoreactivity of the oestrogen or progesterone receptors in women either with or without menorrhagia suggesting that, in addition to endocrine hormones, other factors are involved in the regulation of endometrial proliferation and menstrual blood loss. A total of 35 women were treated with LNG-IUS. After 6 months use of an LNG-IUS, the immunoreactivity of both epithelial and stromal progesterone receptors, as well as those of epithelial Ki-67 declined, and no differences were detectable between the women in the menorrhagia and control groups. Breakthrough bleeding remained a problem for nine (26%) LNG-IUS users, with no association with the pre-treatment amount of bleeding. No significant differences were found in the parameters studied between the women with and without breakthrough bleeding 6 months after insertion of an LNG-IUS.