Women who have their cholesterol checked only to be taken aback at an oddly high level of HDL or LDL might want to check the calendar. Was the appointment at the latter end of the menstrual cycle? The beginning? Their estrogen level at the time might be a factor.
Researchers knew that the estrogen in oral contraceptives and hormone replacement therapy could affect cholesterol levels, but they wanted to know more about the effects of normal estrogen fluctuations inside the body. So they tested lipid levels of 259 women ages 18-44 through two menstrual cycles.
They found that HDL (or good) cholesterol rose as estrogen levels rose, with both topping out at ovulation. Levels of total cholesterol, LDL (or bad) cholesterol and triglycerides fell as this happened.
Ultimately, the researchers -- from the National Institutes of Health -- found, cholesterol levels varied 19% throughout the menstrual cycle. Yes, 19%.
Here's the abstract of the cholesterol-estrogen study, published earlier this summer in the Journal of Clinical Endocrinology & Metabolism, plus the news release from the National Institutes of Health.
The results may not be shocking. After all, they're in line with what we already know about estrogen and cholesterol.
As the American Heart Assn. points out in this Women and Cholesterol explainer: "The female sex hormone estrogen tends to raise HDL cholesterol, and as a rule, women have higher HDL (good) cholesterol levels than men do. Estrogen production is highest during the childbearing years. This may help explain why premenopausal women are usually protected from developing heart disease."
But the size of the variation is worth noting, as the researchers point out, when assessing research results or cholesterol management of individual women. Or as they put it:
"Endogenous estrogen, like exogenous estrogen, appears to have beneficial effects on the lipid profile. Because lipoprotein cholesterol levels vary across the menstrual cycle, cyclic variations in lipoprotein levels may need to be considered in the design and interpretation of studies in reproductive-age women and in the clinical management of women's cholesterol."
-- Tami Dennis / Los Angeles Times