Women's Cholesterol Levels Vary With Menstrual Cycle

National Institutes of Health researchers have shown that women's cholesterol levels correspond with monthly changes in estrogen levels. This natural variation, they suggest, might indicate a need to take into account the phases of a woman's monthly cycle before evaluating her cholesterol measures. On average, the total cholesterol level of the women in the study varied 19% over the course of the menstrual cycle. The findings were published online in The Journal of Clinical Endocrinology and Metabolism.

In a typical cycle, estrogen levels steadily increase as the egg cell matures, peaking just before ovulation. Previous studies have shown that taking formulations which contain estrogen can affect cholesterol levels. However, the results of studies examining the effects of naturally occurring hormone levels on cholesterol have not been conclusive. According to the National Institutes of Health’s National Heart, Lung and Blood Institute, high blood cholesterol levels raise the risk for heart disease.

The researchers found that as the level of estrogen rises, HDL cholesterol also rises, peaking at the time of ovulation. In contrast, total cholesterol and LDL cholesterol levels, as well as triglycerides, declined as estrogen levels rose. The decline was not immediate, beginning a couple of days after the estrogen peak at ovulation. Total cholesterol, LDL cholesterol, and triglyceride levels reached their lowest just before menstruation began.

The study compared estrogen with cholesterol and triglyceride levels among 259 healthy women aged 18 to 44. For 94% of the volunteers, researchers took 14 or more measurements over two menstrual cycles. Women charted the phases of their cycles with at-home fertility monitors, which detect hormone levels that indicate ovulation.

Most of the women were physically active and did not smoke. Only 5% consistently had total cholesterol levels greater than 200 mg/dL, considered borderline high-risk for heart disease. However, cholesterol levels among 19.7% of the women reached 200 mg/dL at least once.

A small subset of obese women over 40 showed greater fluctuation in cholesterol levels during their cycles than did the rest of the group.

Source: National Institues of Health