Identification of the Menstrual Cycle-Associated Factors That Modulate Circulating Lipid Levels in Premenopausal Women

Premenopausal women are at a lower age-adjusted risk of coronary heart disease (CHD) than men or postmenopausal women. This decreased risk of CHD is likely due, in part, to the more favorable lipid profile observed in premenopausal women. The menstrual cycle is associated with the ovarian processes of follicular growth and ovulation, and corpus luteum (CL) development, function, and regression. The steroids estrogen (E2) and progesterone (P4) are secreted from the follicle and CL, which travel via the bloodstream to elicit their effects on target tissues. The production of E2 has been implicated as the menstrual cycle-associated factor underlying the favorable lipid profile as it is known to increase atheroprotective high density lipoprotein and decrease atherogenic low density lipoprotein. However, other factors may play a role such as direct ovarian metabolism of circulating lipids. Furthermore, the role of P4 is unclear and there is some evidence that it may inhibit the beneficial effects of E2. Therefore, we aim to determine the contributions of ovarian metabolism of lipids, independent of the effects of ovarian-derived E2 and P4, to the circulating lipid profile in premenopausal women. Also, we will determine the relationship between E2 and P4, both natural and synthetic forms found in hormonal oral contraceptives, on circulating lipids. With the recent controversial findings of the Women's Health Initiative, further evaluation of the factors underlying menstrual cycle protection from CHD is warranted. This study may have implications for the management of CHD and the use of hormonal therapies in women.