Follicle stimulating hormone (FSH) is a hormone produced in the pituitary gland in both males and females. It works with luteinizing hormone (LH) to regulate development, growth, pubertal maturation, and reproductive processes. In males, FSH activates Sertoli cells for spermatogenesis and inhibin B secretion. In females, FSH initiates follicular growth, particularly for the development of the female gamete in the ovaries.
Elevated FSH levels are an indication of subfertility and/or infertility. Abnormally high FSH levels in females of reproductive age can occur due to premature menopause, poor ovarian reserve, gonadal dysgenesis, Turner syndrome, and lupus. High FSH levels in males can occur in Klinefelter syndrome, castration, and gonadal dysgenesis.
Low FSH levels can also be an indication of infertility. This can result in low sperm production in males, and cessation of menstruation in females. There are various conditions that result in low FSH, including polycystic ovarian syndrome, Kallmann syndrome, hypothalamic suppression, hypopituitarism, and hyperprolactinemia.