Gonadotropin Type in Ovarian Stimulation

Overview

A key challenge facing reproductive biologists is the integration of the knowledge about oocyte-secreted factors into coherent physiological mechanisms of how oocytes govern folliculogenesis, cumulus cell function, and oocyte and embryo development. Although key oocyte-secreted factors have been identified, understanding their modes of action is complicated by multiple interactions between maternal and oocyte signaling molecules, as well as the constantly changing state of physical interactions between the oocyte and its companion somatic cells during folliculogenesis. Thus, the investigators study aimed to determine if there is any relationship between different gonadotropin preparations and oocyte-secreted factor secretion, the endocrine pattern in follicular fluid, and the apoptotic rate in cumulus cells during controlled ovarian stimulation.

The follicular environment is primarily influenced by the type of gonadotropin the follicle is exposed to during the follicular phase. The role of gonadotropins has been especially important in improving the efficiency of in vitro fertilization. Several studies comparing the use of human menopausal gonadotropin (hMG) with recombinant follicle-stimulating hormone (rFSH) have found significant differences in the endocrinological profile and the follicular dynamics. These differences have been related to the human chorionic gonadotropin (hCG)-driven luteinizing hormone (LH) activity added to hMG. Moreover, differences in the proportion of acid residues in FSH molecules should be considered. On the other hand, the main physiological regulatory hormones of follicular survival are the gonadotropins. Suppression of serum gonadotropins leads to massive apoptosis of granulosa cells in developing follicles resulting in atresia; whereas, gonadotropin treatment of early antral and pre-ovulatory follicles prevents this unplanned apoptosis. However, studies using cultured rat granulosa cells have shown that treatments with FSH or LH/hCG are ineffective in preventing spontaneous apoptosis, suggesting neighboring theca cells and local factors produced in the ovary are important for regulation of follicle growth and atresia.