Hormone replacement therapy is associated with improved arterial physiology in healthy post-menopausal women

Oestrogen replacement therapy is associated with a marked reduction in coronary event rates in post-menopausal women. As older age is associated with progressive arterial endothelial damage, a key event in atherosclerosis, we assessed whether hormone replacement therapy (HRT) with oestrogen alone, or oestrogen and progesterone combined, is associated with improved endothelial function in healthy women after the menopause.

Using high resolution external vascular ultrasound, brachial artery diameter was measured at rest and in response to reactive hyperaemia, with increased flow causing endothelium-dependent dilatation (flow-mediated dilatation).

We investigated 135 healthy women; 40 were pre-menopausal (mean +/- SD age/26 +/- 6 years, group 1), 40 were post-menopausal and had never taken HRT (aged 58 +/- 3 years; group 2) and 55 were age-matched post-menopausal women who had taken HRT for > or = 2 years, from within 2 years of the menopause (aged 57 +/- 4 years; group 3). In group 3, 40 women were on combined oestrogen and progesterone and 15 on oestrogen-only HRT.

In group 2, flow-mediated dilatation was significantly reduced compared with group 1 (4.4 +/- 3.4 vs 9.6 +/- 3.6%, P < 0.001), consistent with a decline in arterial endothelial function after the menopause. In group 3, however, flow-mediated dilatation was significantly better than group 2 (6.2 +/- 3.3 vs 4.4 +/- 3.4%, P = 0.01), suggesting a protective effect of HRT. Flow-mediated dilatation was similar in women taking oestrogen alone and in those on combined HRT (5.5 +/- 2.8 vs 6.5 +/- 3.4%, P = 0.40).

Long-term HRT is associated with improved arterial endothelial function in healthy post-menopausal women. This benefit was observed in both the combined hormone replacement and unopposed oestrogen therapy groups. This may explain some of the apparent cardioprotective effect of HRT after the menopause.