HRT and cardiovascular disease.

Hormone replacement therapy (HRT) has profound effects on the cardiovascular system, with plausible biological mechanisms explaining both the benefits and harm. Benefits may result from oestrogen action on metabolic risk factors, such as lipids, glucose and insulin metabolism, as well as direct arterial effects, reducing atherogenesis. Harm may arise from inappropriately high starting doses causing transient increases in coagulation activation and adverse vascular remodelling. Observational studies of HRT suggest that there is a beneficial effect on the incidence of coronary heart disease (CHD). Any benefit of HRT seen in randomized clinical trials appears to be confined to those women within several years of their menopause, and it is clear from the randomized trials that age at initiation is a crucially important consideration. Women initiating HRT within 10 years of menopause onset may achieve cardiovascular benefit, particularly in terms of primary CHD prevention, whilst avoiding risks of stroke and venous thrombo-embolism.