Follicle-stimulating hormone (FSH) is a glycoprotein polypeptide hormone. It stimulates the gonads i.e., testes in males and ovaries in females. It is synthesized and secreted by the anterior pituitary gland's gonadotropic cells and regulates the body's development, growth, pubertal maturation, and reproductive functions. FSH and Luteinizing hormone (LH) operate together in the reproductive system. FSH is a glycoprotein heterodimer consisting of two polypeptide units, alpha and beta. The alpha subunits of Luteinizing hormone (LH), thyroid-stimulating hormone (TSH), and human chorionic gonadotropin (hCG) are identical but their beta subunits vary. High FSH levels and low FSH levels both are diseased states. Premature menopause, poor ovarian reserve, gonadal dysgenesis, Turner syndrome, Klinefelter syndrome, castration and Swyer syndrome are some of the conditions associated with high levels of FSH. Polycystic ovarian syndrome, obesity, hirsutism, infertility, Kallmann syndrome, hypothalamic suppression and hypopituitarism are some conditions related to low levels of FSH. This book unfolds various researches related to the function and use of FSH. These studies can prove to be crucial to the research in the field of reproductive medicine. It will provide comprehensive knowledge on role of follicle stimulating hormone to the readers.