In the midst and even in the aftermath of treatment for breast cancer, it may be difficult to tell whether you have gone into menopause. You may be in the midst of chemotherapy and miss a few periods. Or you may have had a hysterectomy (so your periods have stopped), but you still have your ovaries intact (and you are not sure if you are continuing to ovulate).
Blood tests can tell whether your ovaries are beyond menopause or not. These blood tests measure your levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), proteins made by the brain that stimulate ovulation. If your ovaries are beyond menopause, they no longer respond to FSH and LH, and your brain reacts by sending out even more of these hormones. Blood tests indicating high levels of FSH and LH show your doctors your menopausal status.
Persistent elevated levels of FSH (13–90 milli-international units per milliliter) and LH (15–50 mIU/mL) are consistent with a post-menopausal state. Normal levels of estrogen before menopause peak at 150–300 picograms per milliliter each month (depending on where you are in your menstrual cycle), falling to less than 20 pg/mL after ovarian function declines. In pre- or peri-menopausal women taking tamoxifen, estrogen levels can be significantly increased above normal.