Menstrual Cycle Affects Cholesterol Levels

(August 12, 2010) - When women get tested for their cholesterol levels (Read about "Cholesterol") they, and their doctors, might want to consider where they are in their menstrual cycle. National Institutes of Health researchers say 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 percent over the course of the menstrual cycle. In a typical cycle, estrogen levels steadily increase as the egg cell matures, peaking just before ovulation.

The findings were published online in The Journal of Clinical Endocrinology and Metabolism.

The study authors found that women's total cholesterol levels rise as estrogen levels increase during the monthly menstrual cycle, drop shortly before ovulation, then decrease more rapidly after ovulation occurs.

The researchers found that as the level of estrogen rises, high-density lipoprotein (HDL) cholesterol also rises, peaking at the time of ovulation. HDL cholesterol is believed to be protective against heart disease. (Read about "Coronary Heart Disease")

In contrast, total cholesterol and low-density lipoprotein (LDL) cholesterol levels - as well as another form of blood fat known 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.

"It's more likely cholesterol levels will be elevated in women before ovulation, which could have a particular impact on women whose cholesterol levels are already high," Enrique F. Schisterman, Ph.D., on of the researchers said.