Endometrial response to hormone replacement therapy as assessed by expression of insulin-like growth factor-binding protein-1 in the endometrium

To assess endometrial response to parenteral levonorgestrel in hormone replacement therapy by means of morphological criteria and immunohistochemical staining of insulinlike growth factor-binding protein-1 (IGFBP-1). Endometrial samples were collected from 35 postmenopausal women after 12 to 22 months of continuous combined estrogen-progestin therapy. All subjects were treated with parenteral progestin. A group of 8 women was treated with a subdermal levonorgestrel-releasing implant, and 27 women had a levonorgestrel-releasing intrauterine device (IUD). Sections of formalin-fixed paraffin-embedded biopsies were used for immunohistochemistry and after hematoxylin-eosin staining for routine histologic examination. Atrophic epithelium with pronounced decidual reaction in the stroma was detected by histologic examination in all endometrial samples obtained from 27 women treated with the levonorgestrel-releasing IUD. In contrast, the endometrium was proliferative in seven of eight (87.5%) biopsies obtained from women treated with the levonorgestrel-releasing implant. Immu-noreactive IGFBP-1 was detected in decidualized stromal cells in all endometrial samples obtained during intrauterine levonorgestrel therapy, whereas only one of eight samples obtained from women treated with subdermal levonorgestrel exhibited weak staining for IGFBP-1. Our data show that both the morphological and biochemical response of postmenopausal endometrium to parenteral levonorgestrel was strikingly different, depending on the route of progestin administration, and that the decidual reaction and epithelial atrophy induced by intrauterine levonorgestrel were associated with expression IGFBP-1 in decidualized stromal cells.