Hormone replacement therapy and cardiovascular disease

Observational studies of hormone replacement therapy show coronary heart disease benefit, whereas randomised clinical trials do not. In the latter, this is perhaps because early harm caused by hormone replacement therapy outweighs any later benefit. Early harm may be caused by inappropriately high starting doses for the woman's age, which could cause transient increases in thrombogenesis and adverse vascular remodelling. Later benefit could result from oestrogen action on metabolic risk factors, as well as direct arterial effects reducing atherogenesis. Women in observational studies are younger and starting doses are appropriate for their age. Hormone replacement therapy doses and regimens that benefit coronary heart disease could be formulated and tested.