New Understanding in the Biochemistry of Implantation: Potential Direct Roles of Luteinizing Hormone and Human Chorionic Gonadotropin

Abstract

Luteinizing hormone/human chorionic gonadotropin (LH/hCG) receptors are present in human implantation sites that contain intermediate trophoblasts, decidual cells, and blood vessels. These receptors also are in human endometrial stromal cells, endometrial glands, myometrial smooth muscle, and T lymphocytes. Highly purified exogenous hCG and LH can promote the differentiation of stromal cells into decidua, increase the levels of cyclooxygenase-2 (COX-2) in glandular epithelial cells, decrease the resistance index, increase prostacyclin, decrease thromboxane B2 synthesis in uterine arteries, and inhibit contractions of the uterus. These changes are required for the successful implantation of the blastocyst. Thus, it is likely that LH and hCG directly promote implantation in humans and possibly in other species.