FSH in Serum

Low FSH usually suggests reduced hypothalamic or pituitary drive.

In men, it may be seen with secondary hypogonadism and can impair spermatogenesis and fertility.

In women, it may be seen with hypothalamic or pituitary dysfunction, caloric deficit, low body weight, excessive exercise, and functional hypothalamic amenorrhea.

High FSH usually reflects reduced gonadal feedback.

In men, it is seen with primary testicular dysfunction or impaired spermatogenesis.

In women, it rises physiologically with perimenopause and menopause, and outside that setting may suggest primary ovarian insufficiency, ovarian failure, or Turner syndrome.