Follicle-Stimulating Hormone (FSH)

Follicle-stimulating hormone (FSH) is a pituitary hormone that drives egg development in women and sperm production in men. Your FSH level helps show whether a reproductive concern starts in the ovaries or testes themselves or higher up in the brain.

Ranges vary by cycle phase, menopause, lab, and assay, so compare to the range on your own lab report.

What FSH measures

FSH is released by your pituitary gland, a small structure at the base of the brain that acts as a control center for reproductive hormones. In women it stimulates ovarian follicles, the fluid-filled sacs that hold and mature eggs, and it supports estrogen production. In men it acts on Sertoli cells in the testes to keep sperm production going.

What high or low levels mean

High FSH often means your ovaries or testes are not responding well, so your pituitary raises the signal to compensate. In women this pattern points toward reduced ovarian reserve or the menopausal transition, when levels climb and stay elevated. In men it can suggest primary testicular failure that affects sperm production. Low FSH points the other way, toward a pituitary or hypothalamic problem, and can show up with significant stress, under-fueling, illness, or a pituitary tumor. You should follow up if your result sits well outside your lab range, if it does not fit your age or symptoms, or if you are having trouble conceiving. FSH is rarely read alone. Your clinician will interpret it alongside LH and estradiol or testosterone to see the full picture.

FSH FAQ

Does a high FSH mean I am in menopause?

A single high reading is not a diagnosis. Menopause is usually confirmed after 12 months without a period, and elevated FSH supports the pattern rather than proving it on its own.

When should FSH be tested in my cycle?

For women, day 3 of your cycle is the standard timing, because the follicular phase gives the most comparable baseline before menopause shifts levels higher.

Can FSH help evaluate fertility?

Yes. In women, a day 3 FSH helps gauge ovarian reserve, and in men it helps assess sperm production. It is read with LH and sex hormones rather than on its own.

Read alongside luteinizing hormone, estradiol, and total testosterone for a fuller reproductive and hormonal picture.

Sources

• Cleveland Clinic. Follicle-Stimulating Hormone (FSH).

• Medscape. Follicle-Stimulating Hormone (FSH): Reference Range.