The role of gonadotropins in the follicular phase

Abstract

Folliculogenesis in humans is a lengthy process that involves several regulators. Pituitary gonadotropins play crucial roles in the late stages, particularly in the last 15 days of follicle maturation. During the intercycle rise of follicle-stimulating hormone (FSH), selection of the dominant follicle takes place. This is a complex process that also involves locally produced substances. At the same time, luteinizing hormone (LH) stimulates the synthesis of androgens, which serve as the substrate for the production of estrogens. During the second half of the follicular phase, the follicle becomes dependent on LH. Induction of multiple follicular development by exogenous FSH results in a marked suppression of endogenous LH. For normal follicle maturation, both an LH threshold and an LH ceiling have been considered. In the context of an in vitro fertilization program, application of protocols for ovarian stimulation that will prevent the marked suppression of endogenous LH secretion might provide a better approach to treatment optimization.

Effect of Anti-Müllerian hormone (AMH) and bone morphogenetic protein 15 (BMP-15) on steroidogenesis in primary-cultured human luteinizing granulosa cells through Smad5 signalling

“…Ovarian follicles constitute the functional unit of the human ovary; endocrine signaling via the hypothalamus-pituitarygonadal axis is crucial for its survival, development, maturation and steroidogenic activity [1][2][3]. Nevertheless, local growth factors seem to have a pivotal and synergistic role in these procedures [4,5].…”

Lgr4 Gene Regulates Corpus Luteum Maturation Through Modulation of the WNT-Mediated EGFR-ERK Signaling Pathway

“…A growing body of evidence indicates that ovarian-secreted factors participate in these processes and function as either direct or indirect mediators downstream of LH signaling (5). Epidermal growth factor (EGF) is the founding member of the EGF family which also includes amphiregulin (Areg), epiregulin (Ereg), epigen, betacellulin (Btc), neuregulin and heparin-binding EGF-like growth factor (HB-EGF) (6).…”

Human Chorionic Gonadotropin: The Pregnancy Hormone and More

“…Primordial and primary preantral are considered gonadotropin independent stages of follicular development, since cumulus and theca cells lack FSH and LH receptors. However, studies have demonstrated the presence of FSH and LH receptors from the secondary preantral and from the antral stage onwards, respectively [3]. LH receptors are also present in the theca cells from the secondary preantral stage onwards, while they are lacking FSH receptors.…”