Insulin-like growth factor-binding protein-1: A biochemical marker of endometrial response to progestin during hormone replacement therapy

Objectives: To compare immunohistochemical localization of insulin-like growth factor binding protein-1 (IGFBP-1) in endometrial stromal cells with endometrial morphology during three regimens of continuous combined hormone replacement therapy. Methods: Endometrial samples for morphological examination and immunohistochemical staining with monoclonal antibody against IGFBP-1 were obtained from 30 menopausal women before treatment and after 12 and 24 months of continuous combined hormone replacement therapy. All women received percutaneous estradiol-gel releasing 1.5 mg estradiol daily. Regarding progestins, patients were divided into three groups: one group (n = 15) had a 20 mu g/24 h levonorgestrel-releasing intrauterine device (LNG-IUD); the women in the other two groups received micronised natural progesterone either 100 mg orally (n = 7) or 100-200 mg vaginally (n = 8) daily, 25 days per calendar month, Results: Before treatment the endometrium of all women was atrophic or subatrophic and no IGFBP-1 could be detected in any of the samples which contained enough stromal cells for evaluation. After 12 and 24 months of treatment, epithelial atrophy with decidual transformation in stroma was detected in all specimens in the LNG-IUD group, and IGFBP-1 was localized in decidualized stromal cells in all samples. In the other two groups, no signs of progestin effect were detected by microscopic examination in any of the endometrial samples and IGFBP-1 staining was completely negative in all of them. Conclusion: A striking difference occurred in both morphological and biochemical response in the endometrium of women treated with LNG-IUD compared with those receiving oral or vaginal micronised progesteron during continuous combined HRT. Micronised progesterone at doses used in this study turned out to be ineffective to prevent the proliferative effect of estrogen. Immunohistochemical localization of IGFBP-1 in endometrial stromal cells strongly correlated with decidual reaction in all endometrial specimens exposed to LNG-IUD, suggesting that the immunostaining of IGFBP-I can be used as a means of assessing the strength of progestin effect in the endometrium during HRT.