Expression of pituitary gonadotropic hormone and sex hormones receptors in endometrial cellular components during menstrual cycle

Introduction. The main function of the endometrium is to create the optimal environment for embryo implantation, controlled by multicomponent signaling pathways. They are modulated by progesterone and estradiol acting through related estrogen receptors (ER) and progesterone receptors (PR). Alteration in steroid hormone, follicle-stimulating hormone (FSHR), and luteinizing hormone (LGHR) receptor expression are underlying factors in the development of various reproductive disorders. Therefore, understanding the physiological features of receptors expression and localization in tissues is extremely important for a proper comprehensive assessment of the endometrial condition. Materials and methods. The expression of ER, PR, FSHR, and LGHR in endometrial samples of healthy females from different menstrual periods, who applied for assisted reproductive technologies (ART) due to male infertility, was assessed by immunofluorescence. Results. The increase in immunoreactivity of ER, PR, FSHR, and LGHR in the glands and stroma of the endometrium is initiated during the early proliferation stage and reaches its maximum during the late proliferation stage. Subsequently, ER expression in the glands and stroma gradually decreases throughout the early and middle stages of secretion; PR immunoreactivity in the stroma and FSHR and LGHR in all endometrial components persists throughout the secretion stage. Conclusion. The correspondence between the change of the studied receptors' expression and endometrium structural features at different stages of the menstrual cycle was demonstrated. The increased expression of ER, PR, FSHR, and LGHR in the endometrium at the proliferation stage coincides with the growth period of the uterine body mucosa, and the increased immunoreactivity of PR, FSHR, and LGHR during the secretion stage is associated with its decidual transformation and seems to create conditions for successful implantation and embryo development if pregnancy occurs.