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The effects of hormone replacement therapy on endothelial function in women with Turner's syndrome
N Norman Chan1, Patrick Vallance, Helen M Colhoun
1Centre for Clinical Pharmacology, EURODIAB, Department of Epidemiology and Public Health, University College London, London, UK. nnkachan@aol.com
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 NG-monomethyl-l-arginine, 1, 2, 4 micromol/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.