Primary ovarian insufficiency (POI), also called premature ovarian insufficiency, premature menopause, and premature ovarian failure, is the partial or total loss of reproductive and hormonal function of the ovaries before age 40 because of follicular (egg producing area) dysfunction or early loss of eggs. POI can be seen as part of a continuum of changes leading to menopause that differ from age-appropriate menopause in the age of onset, degree of symptoms, and sporadic return to normal ovarian function. POI affects approximately 1 in 10,000 women under age 20, 1 in 1,000 women under age 30, and 1 in 100 of those under age 40. A medical triad for the diagnosis is amenorrhea, hypergonadotropism, and hypoestrogenism. Physical and emotional symptoms are similar to those seen during menopause and can include hot flashes, night sweats, dry skin, vaginal dryness, irregular or absent menstruation, anxiety, depression, mental fog, irritability, nervousness, decreased libido, and increased autoimmune disruption. The sense of shock and distress on being informed of the diagnosis can be overwhelming. Hormonal therapy with estrogen and progesterone is the first line treatment and is associated with improvement of symptoms and possibly improvement in other parameters such as bone density, mortality and cardiovascular risk. The general treatment is for symptoms, bone protection, and mental health. Although 5 to 10% of women with POI may ovulate sporadically and become pregnant without treatment, others may use assisted reproductive technology including in vitro fertilization and egg donation or decide to adopt or remain childless. The causes of POI are heterogeneous and are unknown in 90% of cases. It can be associated with genetic causes, autoimmune disease, enzyme deficiency, infection, environmental factors, radiation, or surgery in 10%. Two to 5% of women with POI and a premutation in FMR1, a genetic abnormality, are at risk of having a child with fragile X syndrome, the most common cause of inherited intellectual disability. The diagnosis is based on ages less than 40, amenorrhea, and elevated serum follicle-stimulating hormone (FSH) levels. Typical serum FSH levels in POI patients is in the post-menopausal range. Treatment will vary depending on the symptoms. It can include hormone replacement therapy, fertility management, and psychosocial support, as well as annual screenings of thyroid and adrenal function.

Reference
Wiki: Premature ovarian insufficiency