The gonadotropin follicle-stimulating hormones (FSH), follitropin alfa (Gonal-F) and follitropin beta (Follistim), are produced in the anterior lobe of the pituitary gland. FSH can function in two ways. On the one hand, it causes increased spermatogenesis in men. On the other hand, in concert with estrogen and luteinizing hormone (LH), it stimulates follicular growth and development in women. Consequently, FSH may be useful in the treatment of infertility. FSH is a member of a superfamily of proteins, all structurally related, which includes LH, chorionic gonadotropin, and thyroid-stimulating hormone (TSH).