The mechanisms that mediate the cardioprotective action of
steroid hormones in postmenopausal women are poorly understood. To study the inter-relationship between female
steroid hormones and cardiac
natriuretic peptides, plasma levels of
atrial natriuretic peptide (
ANP) and
brain natriuretic peptide (BNP) were measured in postmenopausal women, both before and after oestrogen replacement
therapy. A total of 22 healthy postmenopausal women (mean age 51.9+/-4.6 years) were enrolled in the study; all had been postmenopausal for at least 1 year and all reported climacteric symptoms accompanied by increased levels of
follicle-stimulating hormone (>30 m-i.u./ml) and
luteinizing hormone (>20 m-i.u./ml), and a reduction in
oestradiol (<25 pg/ml). All women were given
hormone replacement therapy with transdermal
oestradiol, either patch (50 microg/24 h) or gel (1 mg/day), cyclically combined with oral dihydrogesterone (10 mg/day for 12 days/month, on days 19-30 of the month).
ANP and BNP were measured directly in plasma samples with specific and sensitive immunoradiometric assays before and after
hormone replacement therapy (transdermal
oestradiol combined with oral dihydrogesterone).
Body weight, arterial blood pressure and echocardiographic examination values did not change after
hormone replacement therapy. As expected, serum
oestradiol increased significantly and
gonadotropins decreased as an effect of the
hormone replacement therapy. On average, both
ANP and BNP had increased significantly after 3 months of
hormone replacement therapy [
ANP: before treatment, 17.6+/-9.6 pg/ml; after, 23.6+/-5.6 pg/ml (P=0.0173); BNP: before treatment, 12.6+/-10.2 pg/ml; after, 19.8+/-14.0 pg/ml (P<0.0001)]. Our study indicates that
hormone replacement therapy for a period of 3 months induces a rise in the circulating levels of cardiac
natriuretic hormones in postmenopausal women. Our data also suggest the working hypothesis that cardiac
natriuretic peptides may play an important role in mediating the cardioprotective effects of female
steroid sex hormones in women throughout life.