Cholesterol Levels Vary Throughout the Menstrual Cycle
The fluctuation of hormones during the female menstrual cycle may have more impact on cardiovascular health than researchers previously thought. While doctors have known that the cessation of estrogen production after menopause can increase a woman’s risk for heart disease, even the monthly cyclical variations of hormones play an important role. Researchers have found that serum lipid levels (cholesterol) vary throughout the menstrual cycle and could play an important role on determining the best time for screening.
Cholesterol Screening Should Take Into Account Estrogen Variations
It is known that exogenous estrogen - that which is obtained outside of the body such as through hormone therapy or birth control pills - affects cholesterol levels in women. The researchers from Eunice Kennedy Shriver National Institute of Child Health and Human Development conducted the most recent study to determine the effect of endogenous estrogen (that which is made by the body naturally) and lipid profile levels.
The study included 259 healthy, regularly menstruating women aged 18 to 44 who were not taking oral contraceptives or other medications. The majority of the women had normal levels of cholesterol, did not smoke, and were physically active. The women charted their menstrual cycles at home using fertility monitors that detect hormone levels. The researchers tested total cholesterol levels, as well as HDL, LDL and triglycerides, between eight and fourteen times per menstrual cycle for one or two cycles.
Overall, the women’s total cholesterol levels varied by 19% over the course of a month. The researchers found that as estrogen levels rise, HDL (“good”) cholesterol also rises. HDL cholesterol peaked when endogenous estrogens peaked at mid-cycle (ovulation). Total cholesterol, LDL cholesterol and triglycerides began to decline at mid-cycle and were lowest just before the onset of menstruation.
Although the changes in total and LDL cholesterol levels were modest (only 5 to 8%), the authors write, some women actually crossed over from normal levels into that which is considered high.
The authors suggest that for a clearer picture of a pre-menopausal woman’s cholesterol levels, doctors may need to take several readings before deciding whether the patient needs interventions, such as cholesterol-lowering medications. To make the readings more consistent and reliable, doctors should offer the test at the same time each month for a couple of cycles, says study co-author Enrique F. Schisterman.
Enrique F. Schisterman, Ph.D., chief, Epidemiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development; Jennifer Glueck, an assistant professor, clinical medicine, division of endocrinology, diabetes and metabolism, University of Miami Miller School of Medicine; Aug. 10, 2010, Journal of Clinical Endocrinology and Metabolism, online at http://jcem.endojournals.org.