Isolated follicle-stimulating hormone deficiency (IFSHD) can be caused by mutations in the gene encoding the beta chain of follicle-stimulating hormone (FSH). FSH is essential for normal puberty and fertility in females, particularly ovarian follicular development beyond the antral stage. In males, FSH is necessary for normal spermatogenesis and when FSH function is completely absent, infertility occurs. With partial FSH deficiency in males, spermatogenesis is affected, but fertility may still be possible.
