What does the Follicle-Stimulating Hormone test measure?

Why is Follicle-Stimulating Hormone measured?

FSH is central to evaluating the hypothalamic-pituitary-gonadal axis. A raised FSH indicates reduced gonadal feedback, as in primary ovarian insufficiency, menopause, or primary testicular failure, whereas a low or inappropriately normal FSH in the face of low gonadal hormones points to a hypothalamic or pituitary (secondary) cause. It is interpreted with LH and the relevant gonadal steroids, and timing within the menstrual cycle is essential in women.

Reference ranges

Standard reference

Highly cycle-phase, sex- and age-specific. Premenopausal follicular phase ~3.5–12.5 mIU/mL; postmenopausal ~25.8–134.8 mIU/mL; adult men ~1.5–12.4 mIU/mL # REVIEWER FLAG: FSH intervals are strongly phase-, sex- and age-banded and assay-specific — reviewer to confirm against Access Medical Laboratories assay-specific ranges before publication.

Functional medicine optimal

Early follicular phase: <8 mIU/mL (functional medicine ovarian reserve adequacy threshold, though AMH provides superior sensitivity for ovarian reserve). # REVIEWER FLAG: FSH optimal threshold for ovarian reserve varies by fertility specialist and is supplementary to AMH in current clinical practice.

Units

mIU/mL, IU/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.