Homocysteine in postmenopausal women and the importance of hormone replacement therapy.

Homocysteine (Hcy) has been shown to damage the vascular endothelial cells, contributing to atherothrombosis. The increase in plasma Hcy levels with natural menopause suggests a close relationship between Hcy metabolism and estrogen status and proposes one of the mechanisms through which menopause unfavorably affects cardiovascular disease risk in women. In addition to the prevention of osteoporosis, hormone replacement therapy (HRT) lowers Hcy levels in postmenopausal women. The first report by van der Mooren et al., demonstrated in an uncontrolled study a significant reduction (11%) in fasting serum Hcy level after 6 months of treatment with sequentially combined estradiol-dydrogesterone therapy in 21 healthy postmenopausal women. This effect was particularly evident in women with initially elevated baseline serum Hcy concentrations. Similar results were found in other studies in which women were treated with various transdermal as well as oral HRT regimens, although two studies could not confirm these findings. All these studies were uncontrolled, and three of them consisted of a relatively small number of participants. Therefore, they remained inconclusive. Three randomized controlled trials on HRT and Hcy were published to date, confirming that postmenopausal HRT reduces circulating levels of Hcy. Current and recent HRT use is associated with a slight increased risk of breast cancer. As a result of this, research has centered on finding compounds that can prevent the consequences of estrogen deficiency, without the potential risk of HRT. Raloxifene, referred to as a Selective Estrogen Receptor Modulator (SERM), has the potential as a viable alternative to HRT. Recently, two randomized controlled trials demonstrated that raloxifene lowers plasma Hcy levels in postmenopausal women, similar to the reduction obtained with HRT. Little is known about the mechanisms underlying the HRT-associated lowering of plasma Hcy. Proposed mechanisms relate to an increase in kidney methionine synthase activity or may be related to the transamination of methionine. We conclude that HRT decreases plasma Hcy levels in postmenopausal women and that the strongest reductions can be achieved in women with the highest concentrations.