There are some obvious reasons why a woman might not have periods. If a woman has gone through menopause, not gone through puberty, is pregnant, is using the birth control pill continuously, or has had an ablation or a hysterectomy, then obviously menstrual periods will be absent.
However, if you are in the reproductive years and have gone through puberty, are not on the pill and your periods stop, that's a concern. In fact if they become infrequent to the point that they are happening less often than every 3 months, that's a concern.
It's a concern because it nearly always signals a serious underlying disease. Although rare, pituitary gland (brain) tumors and ovarian tumors can cause periods to stop. Endocrine problems such as thyroid and adrenal problems can cause periods to stop, medications can cause periods to stop, and premature menopause can cause periods to stop. Sometimes serious female athletes stop producing adequate pituitary hormones to cycle each month. This is a concern because their estrogen levels drop very low and they are at risk for osteoporosis.
However, by far and away the most common cause of periods, is polycystic ovarian syndrome. Click here for more information about PCOS, and its diagnosis and treatment. In fact, PCOS is a symptom of serious underlying metabolic disease and insulin resistance that can lead to diabetes, heart disease, stroke, high blood pressure, high cholesterol, and estrogen related cancers. It should always be treated.
Estrogen levels are high, relative to progesterone, when you have PCOS. Estrogen causes the lining of your uterus that sheds and bleeds every month (the endometrium) to grow fast and at times even abnormally. It is kept in check by progesterone, which is the menstrual timekeeper and lets your body have a period after each ovulation. But if you are not ovulating, you do not produce progesterone, and the unchecked estrogen can cause polyps, precancers and cancers of your endometrial lining. Think of estrogen as the fertilizer of the endometrium, and progesterone as the lawn mower. You need both.
There are two kinds of estrogen receptors: Estrogen receptor alpha and estrogen receptor beta. The alpha kind is found on your uterus and your breasts. The beta kind is on your heart, bones, brain, and blood vessels, mostly. It is healthy to have few alpha receptors (since they have been implicated in breast and uterine cancer), and lots of beta receptors (they have been implicated in heart disease prevention and breast cancer prevention). Insulin resistance and PCOS increase the alpha receptors and decrease the beta receptors. So it is important to treat the underlying insulin resistance that causes this problem.
With PCOS, testosterone levels can be high and can cause facial hair growth, male pattern balding, acne, and large pores.
PCOS is exacerbated by weight gain and obesity. It has made the diagnosis of menopause more difficult. With PCOS, periods stop but typically estrogen levels remain high, so you really don't get the classic menopausal symptoms. In the meantime, progesterone levels do drop. Essentially this sets you up for estrogen related cancers (endometrial and breast, primarily). So it is important to determine if this really is menopause, or if it is PCOS because of the weight gain that often occurs in the years leading up to the menopause.
Debra Ravasia, updated 2017