Follicle-stimulating hormone (9002-68-0)

 Follicle-Stimulating Hormone (CAS NO.9002-68-0) (FSH) is a hormone found in humans and other animals. It is synthesized and secreted by gonadotropes of the anterior pituitary gland. It regulates the development, growth, pubertal maturation, and reproductive processes of the body. Follicle-Stimulating Hormone and Luteinizing hormone (LH) act synergistically in reproduction. It is a glycoprotein. Each monomeric unit is a protein molecule with a sugar attached to it; two of these make the full, functional protein. Its structure is similar to those of LH, TSH, and hCG. The protein dimer contains 2 polypeptide units, labeled alpha and beta subunits. The alpha subunits of LH, FSH, TSH, and hCG are identical, and contain 92 amino acids. The beta subunits vary. FSH has a beta subunit of 118 amino acids (FSHB), which confers its specific biologic action and is responsible for interaction with the FSH-receptor. The sugar part of the hormone is composed of fucose, galactose, mannose, galactosamine, glucosamine, and sialic acid, the latter being critical for its biologic half-life. The half-life of FSH is 3-4 hours.
Effects in females: FSH stimulates the growth and recruitment of immature Ovarian follicles in the ovary. The cohort of small antral follicles is normally sufficiently in number to produce enough Inhibin B to lower FSH serum levels.In addition, there is evidence that gonadotrophin surge-attenuating factor produced by small follicles during the first half of the follicle phase also exerts a negative feedback on pulsatile luteinizing hormone (LH) secretion amplitude, thus allowing a more favorable environment for follicle growth and preventing premature luteinization.(As a woman nears perimenopause the number of small antral follicles recruited in each cycle diminishes and consequently insufficient Inhibin B is produced to fully lower FSH and the serum level of FSH begins to rise.)
Effects in males: FSH stimulates maturation of seminiferous tubules and spermatogenesis ;FSH enhances the production of androgen-binding protein by the Sertoli cells of the testes by binding to FSH receptors on their basolateral membranes, and is critical for the initiation of spermatogenesis.