Estrogens, progestins and lipid metabolism.

OBJECTIVES: To review some aspects in the recent literature related to the effects of postmenopausal estrogen and progestin use on major plasma lipoprotein risk factors for coronary heart disease (CHD).
METHODS: Collection of relevant information from medical journals, and by the use of Medline and Current Contents.
RESULTS: The beneficial effects of estrogen (LDL cholesterol reduction and HDL cholesterol elevation) are well established. The effects on HDL are modified to different degrees by progestins, depending on the androgenic properties of the latter: the 'sex steroid sensitive' HDL2 subfraction is decreased by nortestosterone derived progestins with androgenic activity. Recently developed methodology employing stable isotopes has helped to clarify underlying mechanisms. Progestins alone, as well as estrogen-progestin combinations have been shown to reduce the plasma levels of Lp(a), another lipoprotein risk factor for CHD. According to one study, estrogen administered alone had a similar effect.
CONCLUSIONS: The effects of hormone replacement therapies on lipid metabolism have been partly established and investigations on the underlying mechanisms are being published. This information will be useful for developing new replacement regimens with more protection against CHD and less adverse effects.