Those who have or are at risk for cardiovascular disease regular have their lipid profiles checked, e.g. cholesterol and triglycerides. Although not given much emphasis, the timing of lipid check up may be important – especially in women. Previous studies have shown that estrogen-containing medications for women – for example, oral contraceptives or menopausal hormone therapy, have been shown to influence cholesterol levels in the blood. Fluctuation in level of estrogen results in fluctuating levels of blood lipids, including high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol and triglycerides.
Results of a recent study funded the National Institutes of Health indicate that natural levels of estrogen in the blood, i.e. variations during the menstrual cycle can also affect cholesterol levels. “In a typical cycle, estrogen levels steadily increase as the egg cell matures, peaking just before ovulation…as the level of estrogen rises, high-density lipoprotein (HDL) cholesterol also rises, peaking at the time of ovulation”. HDL cholesterol is the so-called “good cholesterol” and believed to be beneficial to heart health.
“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.”
LDL (aka bad cholesterol) and triglycerides are bad for the heart. The study results showed that cholesterol levels of women can fluctuate up to 19% during an ovulation cycle.
The researchers believe that when testing for lipids, in the blood, the timing in relation to a woman’s menstrual cycle should be taken into consideration. A test performed close to the point of ovulation can give a false picture of a woman’s lipid profile.
When a test shows high levels of total and LDL cholesterol, a confirmatory test is usually performed. When a patient is tested during the end of her cycle, cholesterol levels are low – misleadingly – that the need for an additional test to confirm a high cholesterol reading might be skipped. Thus, the diagnosis of hypercholesterolemia might be missed.
According to study author Enrique F. Schisterman:
High levels of LDL and cholesterol and triglycerides are risk factors for heart disease.
Photo credit: MenstrualCycle2_en.svg: Isometrik