Effects of Long-Term Estrogen Replacement Therapy Versus Combined Hormone Replacement Therapy on Nitric Oxide-Dependent Vasomotor Function

• Published in: The journal of clinical endocrinology and metabolism Vol. 88; no. 9; pp. 4348 - 4354
• Main Authors: Jokela, Hannu, Dastidar, Prasun, Rontu, Riikka, Salomäki, Anne, Teisala, Klaus, Lehtimäki, Terho, Punnonen, Reijo
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Endocrine Society 01-09-2003; Copyright by The Endocrine Society
• Subjects: Aged; Aorta, Abdominal - drug effects; Biological and medical sciences; Carotid Arteries - diagnostic imaging; Carotid Arteries - drug effects; Cholesterol, HDL - blood; Dinoprost - blood; Drug Combinations; Endothelium, Vascular - drug effects; Endothelium, Vascular - metabolism; Estradiol - analogs & derivatives; Estradiol - therapeutic use; Estrogen Replacement Therapy; Estrogens - therapeutic use; Female; Hemodynamics - drug effects; Hormones. Endocrine system; Humans; Levonorgestrel - therapeutic use; Lipid Peroxidation - drug effects; Lipids - blood; Medical sciences; Middle Aged; Muscle, Smooth, Vascular - diagnostic imaging; Muscle, Smooth, Vascular - physiology; Nitric Oxide - blood; Nitric Oxide - physiology; Pharmacology. Drug treatments; Ultrasonography; Human; Replacement therapy; Estrogen; Long term; Biological activity; Vasomotor reflex; Treatment withdrawal; Nitric oxide; Carotid; Postmenopause; Aorta; Female; Flow velocity; Hormone replacement therapy; Progesterone; Comparative study
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jc.2003-030029

Postmenopausal hormone replacement therapy (HRT) with estrogen may increase production of the predominant endothelium-derived vasodilator nitric oxide (NO) and consequently improve vascular reactivity. In contrast, concurrent progestin therapy may oppose this beneficial effect. We studied the effect of long-term estrogen HRT and combined HRT on vasomotor function and on plasma nitrate, which reflects the amount of NO in the circulation. As lipid peroxidation affects NO production and impairs endothelial function, we also measured the amount of the in vivo lipid peroxidation marker urinary 8-iso-prostaglandin F2α. The study group comprised 15 women receiving estradiol valerate HRT (mean age, 56 yr; treatment duration, 10.5 yr) and 15 women receiving combined HRT with estradiol valerate and levonorgestrel (mean age, 58 yr; treatment duration, 11.3 yr). The peak flow velocity (PFV) and pulsatility index of the common carotid and internal carotid artery and the abdominal aorta were measured by ultrasonography after long-term HRT (baseline), after a 4-wk pause and again 3 wk after reintroducing HRT. A statistically significant interaction between the groups and time points was observed in the PFV of the internal carotid artery (P = 0.011). In women taking estradiol valerate, the PFV values decreased significantly after withdrawal of HRT (P = 0.007) and increased again to the baseline level after reintroduction of therapy (P < 0.001). In women receiving combined HRT, the PFV remained stable over all study periods. At baseline, the PFV of women taking estradiol valerate correlated with the plasma nitrate concentration in the common carotid artery (r = 0.646; P = 0.009) and in the abdominal aorta (r = 0.579; P = 0.024). For pulsatility index and urinary 8-iso-prostaglandin F2α excretion, there were no significant differences between the groups. Our results suggest that the favorable effects of long-term estrogen treatment on blood flow are at least partly mediated through NO. The addition of levonorgestrel to the treatment regimen appears to abolish this effect.