Consider the menstrual cycle when evaluating lipid levels. As estrogen levels rise during the menstrual cycle, so does the level of high-density lipoprotein cholesterol, which peaks at ovulation. And as estrogen peaks, low-density lipoprotein (LDL) cholesterol and triglyceride levels fall, according to a report in the September Journal of Clinical Endocrinology and Metabolism. Hormone and blood lipid levels were measured in 259 healthy women ages 18 to 44 years over two menstrual cycles. Approximately 14 measurements were taken in each woman, most of whom were physically active; only 5% had baseline total cholesterol levels higher than 200 mg/dL (borderline high), but 20% reached 200 mg/dL at least once during the study. Levels of total cholesterol, LDL cholesterol, and triglycerides were lowest just before menstruation started. The results suggest that variations in lipoprotein cholesterol levels "have clinical implications regarding the appropriate timing of lipoprotein cholesterol measurement during the [menstrual] cycle," the authors write.