The effects of hormone replacement therapy on endothelial function in women with Turner's syndrome

Objectives To examine the effect of hormone replacement therapy (HRT) on endothelial function of forearm resistance vessels in women with Turner's syndrome. Design Subjects were studied on three occasions: on their usual HRT (study 1), then after 6 weeks off HRT (study 2) and finally after a further 6 weeks on HRT (study 3). Patients Seven young women with Turner's syndrome were studied. Measurements Forearm blood flow in response to intrabrachial infusion of bradykinin, 10, 30, 100 pmol/min (endothelium-dependent vasodilator), glyceryl trinitrate, 4, 8, 16 nmol/min (GTN; endothelium-independent vasodilator), noradrenaline, 60, 120, 240 pmol/min (NA, alpha-adrenergic receptor agonist) and N(G)-monomethyl-L-arginine, 1, 2, 4 mumol/min (L-NMMA; NO synthase inhibitor) was assessed by bilateral venous plethysmography. Results The vasodilator response to bradykinin, expressed as the within-subject mean difference in area under the dose-response curve between study 2 and study 1, was significantly diminished (-744.2+/-287.2, P=0.04) but improved 6 weeks after HRT recommencement. However, there was no significant change in response to GTN (between study 2 and study 1, 189.5+/-247.8, P=0.47). The vasoconstrictor response to L-NMMA was also diminished in study 2 when compared to study 1 (-100.4+/-35.4, P=0.039) and was restored after HRT was recommenced (between study 3 and study 2, 117.5+/-69.3, P=0.17) whereas there was no significant difference in response to NA between study 2 and study 1 (76.7+/-50.6, P=0.18) or study 3 and study 2 (-70.8+/-71.1, P=0.38). Conclusions HRT improves endothelial function in women with Turner's syndrome.