Premature Ovarian Insufficiency (POI)

Premature ovarian insufficiency (POI) is the loss of normal ovarian function before age 40. Periods stop or become irregular, FSH rises, and the ovaries make less estrogen. Current international guidelines diagnose POI when two criteria are met before age 40. Periods have stopped or become irregular for at least 4 months. An FSH blood test is above 25 IU/L.¹ A repeat FSH test 4 to 6 weeks later helps when the first result is unclear.¹ POI differs from diminished ovarian reserve (DOR), in which the ovaries hold fewer eggs but still release them. It also differs from natural menopause, which usually begins around age 50 or 51. Menopause often occurs between ages 45 and 55.

Estimates of how common POI is vary by study. Older studies found POI in about 1 in 100 women under 40. Recent studies report a rate of about 3.5%. Known causes include autoimmune disease, genetic changes, and damage from chemotherapy or radiation. Among single-gene causes, the one found most often is the fragile X premutation. In most cases, the cause remains unknown. AMH testing can show a decline in ovarian reserve before FSH rises. It may help identify women moving toward POI. AMH values, however, vary widely from woman to woman.² Many women with POI still ovulate from time to time. For that reason, the word "insufficiency" replaced the older word "failure."

POI care has two main health goals. The first is protecting bone and heart health with estrogen replacement. The second is checking the thyroid and adrenal glands for autoimmune disease, which is more common in women with POI.¹ POI affects the whole hormonal axis. A full workup therefore avoids treating a high FSH in isolation. Ovarian activity can return, and with it a chance of natural conception.¹ Finding and supporting that window matters, within an ovarian reserve framework.