Menopause is usually a natural process. But certain surgical or medical treatments or medical conditions can bring on menopause earlier than expected. These include:

Hysterectomy.

A hysterectomy that removes your uterus, but not your ovaries, usually doesn't cause menopause. Although you no longer have periods, your ovaries still release eggs and produce estrogen and progesterone. But an operation that removes both your uterus and your ovaries does cause menopause, without any per menopausal phase. Instead, your periods stop immediately, and you're likely to have hot flashes and other menopausal signs and symptoms.

Chemotherapy and radiation therapy. These cancer therapies can induce menopause, causing symptoms such as hot flashes during the course of treatment or within three to six months.

Premature ovarian failure.

Approximately 1 percent of women experience menopause before age 40. Menopause may result from premature ovarian failure — when your ovaries stop working before age 40 — stemming from genetic factors or autoimmune disease, but often no cause can be found.

When to seek medical advice

It's important to see your doctor during both p menopause and post menopause for preventive health care as well as care of medical conditions that may occur with aging.

If you've skipped a period but aren't sure you've started menopause, you may want to see your doctor to determine whether you're pregnant. He or she may take a medical history, do a pelvic examination and, if appropriate, order a pregnancy test.

Always seek medical advice if you have bleeding from your vagina after menopause.

Screening and diagnosis

The signs and symptoms of menopause are enough to tell most women they have begun going through the transition. If you have concerns about irregular periods or hot flashes, talk with your doctor. In some cases further evaluation may be recommended.

Under certain circumstances, your doctor may check your level of follicle-stimulating hormone (FSH) and estrogen (estradiol) with a blood test. As menopause occurs, FSH levels increase and estradiol levels decrease. Your doctor may also recommend a blood test to determine your level of thyroid-stimulating hormone, because hypothyroidism can cause symptoms similar to those of menopause.