Hormones

Key Biological Properties: FSH is a heterodimeric glycoprotein composed of two subunits, alpha and beta. The alpha subunit is common to other glycoprotein hormones like luteinizing hormone (LH), thyroid-stimulating hormone (TSH), and human chorionic gonadotropin (hCG), while the beta subunit confers its specific biological activity .

Expression Patterns and Tissue Distribution: FSH is primarily expressed in the anterior pituitary gland. Its receptor, FSH receptor (FSHR), is predominantly found in the gonads, including the ovaries in females and the testes in males .

Primary Biological Functions: FSH is essential for the maturation of germ cells in both males and females. In females, it stimulates the growth of ovarian follicles, leading to the production of estrogen. In males, it promotes spermatogenesis by acting on Sertoli cells .

Role in Immune Responses and Pathogen Recognition: While FSH is primarily known for its role in reproduction, emerging research suggests it may also have roles in modulating immune responses, although this area requires further investigation .

FSH exerts its effects by binding to the FSH receptor (FSHR), a G protein-coupled receptor located on the surface of target cells in the gonads. This binding activates multiple signaling cascades, including the cAMP/protein kinase A (PKA) pathway, which regulates cell metabolism and sex steroid production. Other pathways involved include the extracellular-regulated kinases (ERK1/2) and phosphatidylinositol-4,5-bisphosphate 3-kinases (PI3K)/protein kinase B (AKT) pathways .

The expression and activity of FSH are tightly regulated by several mechanisms. Gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates the release of FSH. Inhibin, produced by the gonads, provides negative feedback to the pituitary to inhibit FSH secretion. Additionally, activin enhances FSH secretion. Post-translational modifications, such as glycosylation, also play a role in regulating FSH activity .

Biomedical Research: FSH is widely used in research to study reproductive physiology and endocrine disorders.

Diagnostic Tools: Measurement of FSH levels is crucial in diagnosing reproductive health issues, such as infertility, menopause, and pituitary disorders .

Therapeutic Strategies: Recombinant FSH is used in assisted reproductive technologies (ART) to stimulate ovarian follicle development in women undergoing in vitro fertilization (IVF). It is also used in treating male infertility by enhancing spermatogenesis .

FSH plays a vital role throughout the life cycle, from fetal development to aging. During fetal development, FSH and LH levels peak mid-pregnancy, contributing to the maturation of the first ovarian follicle or seminiferous tubule. During puberty, FSH levels rise, triggering sexual maturation. In adulthood, FSH regulates the menstrual cycle in females and spermatogenesis in males. In aging, changes in FSH levels can indicate the onset of menopause in females and declining reproductive function in males .