CYCLIC CHANGES IN LIPOPROPROTEIN AND APOLIPOPROTEIN LEVELS DURING THEMENSTRUAL-CYCLE IN HEALTHY PREMENOPAUSAL WOMEN ON A CONTROLLED DIET

Lipoprotein, apolipoprotein (ape), and hormone levels were measured in 12 healthy women over three consecutive menstrual cycles; one free-li ving and two under controlled dietary conditions. Serum hormone levels were measured to identify menstrual cycle phases (menses, early folli cular, late follicular, and midluteal). After stabilization for one cy cle on the controlled diet, ANOVA modeling of the second controlled-di et cycle revealed that low-density lipoprotein (LDL) cholesterol level s in the midluteal phase were significantly lower (by 7%) than in the early follicular phase. High-density lipoprotein (HDL) cholesterol lev els during the late follicular phase were higher (by 6%) than menses l evels. Differences in the HDL-cholesterol and apoA-I fluctuations resu lted in a higher proportion of HDL-cholesterol to apoA-I during the la te follicular phase than that during the menses phase. The ratios of L DL cholesterol/HDL cholesterol and apoB/apoA-I in the early follicular phase were greater by 5.6% and 6.0%, respectively, than those in the midluteal phase. Fluctuations in total cholesterol, triglyceride, apoA -I, and apoB did not reach significance. Thus, the cyclic fluctuations of LDL and HDL cholesterol need to be considered in the screening and medical monitoring of women with borderline lipoprotein levels, as we ll as in the design and the interpretation of results of studies invol ving premenopausal women.