Objectives and design: Hormone replacement therapy (HRT) in postmenopausal women may reduce the cardiovascular risk. A dominant protective role of transforming growth factor beta (TGF-beta1) on coronary arteries has been proposed. Lp(a) lipoprotein may block the activation of latent TGF-beta1. Given this background, we examined the effects of HRT on TGF-beta1 and Lp(a) lipoprotein in 99 postmenopausal women. The women had angiographically documented coronary heart disease (CHD) and were randomized to either sequential transdermal 17beta-oestradiol for 14 weeks and then medroxyprogesterone (MPA) for 14 days (HRT) or to a control group (C).
Results: Serum levels of TGF-beta1 were increased in the HRT group compared with the C group after 3 months' treatment and this effect was sustained after 12 months. There was a significant reduction in Lp(a) lipoprotein serum levels after 3 months' treatment in the HRT group compared with the C group. However, after 12 months, no significant difference in changes in Lp(a) lipoprotein serum levels was detected between the two groups.
Conclusion: The novel observation that transdermal 17beta-oestradiol in postmenopausal women increases levels of TGF-beta1 and lowers the concentration of Lp(a) lipoprotein suggests yet another possible mechanism for the cardioprotective effect of HRT. Whereas combination therapy of oestradiol and MPA preserves the beneficial effect on TGF-beta1, it reduces the unopposed oestradiol effects on Lp(a) lipoprotein.