Premature menopause occurs before the age of 40. It is now called primary ovarian insufficiency. It occurs in about 1% of the population. It can be spontaneous, or induced. Induced premature menopause can be caused by removing the ovaries because of a medical problem, such as endometriosis, or from chemotherapy and/or radiation therapy. Menopause induced by chemotherapy often is not permanent, and the ovaries can recover, resulting in the return of menstrual cycles which may or may not be regular. Pregnancy can occur. If the ovaries are removed surgically it is called surgical menopause, and results in a rapid decline of hormone levels unless hormone replacement is immediately begun.
Sometimes the decline in ovarian function is early, but not complete. It is often found at the time of a fertility evaluation, when a women is unable to conceive. Her menses may begin to become irregular in her late 30's, and she is found to have an elevated FSH when her ovulatory function is evaluated. Women with ovarian insufficiency will have follicles that may ovulate intermittently, and they may conceive. It is thought that 5-10% conceive spontaneously. It is not unusual that women with ovarian insufficiency will not respond to stimulation when taking fertility drugs.
Sometimes premature menopause can occur when a women has a hysterectomy when her ovaries remain, or a uterine artery embolization. The theory is that blood flow to the ovary is disrupted, which diminishes ovarian function.
Among the causes of ovarian insufficiency are genetics, autoimmune factors, environmental injury, or metabolic factors. Approximately 80% of the time the cause is not known. Between 4-33% of the time there is a familial component. About 10% of women with ovarian insufficiency will has a family history. Her mother's age at menopause is the most reliable predictive factor.
Fragile X syndrome is related to ovarian insufficiency. Autoimmune causes are often related to associated thyroid or adrenal dysfunction.
The evaluation of premature menopause usually will be done when a women who is in her late 30's begins to experience abnormal menstrual cycles or lack of cycles. An FSH may be obtained as the first test, usually done on the third day of the menstrual cycle. An elevated antimuellerian hormone level, or a decreased ovarian follicle count are additionally obtained. Additionally, a hormonal evaluation including a serum prolactin, thyroid stimulating hormone, and and estradiol level should be obtained.