Mechanisms whereby oestrogens influence arterial health.

Coronary heart disease (CHD) is uncommon in premenopausal women compared with men of similar age, but its incidence increases after the menopause to reach that of men. There is now good population-based evidence that hormone replacement therapy (HRT) in postmenopausal women reduces the incidence of CHD, perhaps by up to 50%. Oestrogens have a beneficial effect on arterial health in many different ways. HRT may both reduce the risk of atheroma formation and improve arterial function. Depending on the formulation, HRT can lower LDL and triglycerides, and increase HDL. Oestrogen may also produce qualitative as well as quantitative improvements in lipoproteins. It can improve insulin resistance and hence carbohydrate metabolism, and may enhance fibrinolysis rather than coagulation. Thus these effects of HRT on risk factor for CHD will reduce the risk of atheroma development and progression. Oestrogen has direct effects on blood vessels and improves vascular function through various mechanisms including endothelium-dependent and calcium-dependent processes. HRT should therefore now be considered for use in postmenopausal women with established CHD risk.