Estrogen improves endothelial function - Discussion

Purpose: To determine the effect of estrogen on endothelium-dependent relaxation in the cutaneous microcirculation of women. Methods: Three groups of women participated in the study. Group 1 (n = 20) was premenopausal and had a mean age of 39 years (range 24-50 years). Group 2 (n = 9) was postmenopausal and had a mean age of 58 years (range 53-65 years). Group 3 (n = 11) was postmenopausal and taking estrogen replacement therapy; the mean age was 53 years (range 43-58 years). Eleven women in group 1 underwent testing twice, once during menstruation (mean serum estradiol level 73 ± 30 pg/ml) and once during midcycle (mean serum estradiol level 268 ± 193 pg/ml; p = 0.003). Single-point laser Doppler ultrasound and laser Doppler imaging with a scanner were used to measure vasodilatation in the forearm skin in response to iontophoresis of 1% acetylcholine (endothelium dependent) and 1% sodium nitroprusside (endothelium-independent smooth muscle relaxant). Results: All three groups were matched for body mass index and fasting glucose, total, high-density lipoprotein, and low-density lipoprotein cholesterol and triglyceride levels. All women had normal blood pressure, and none smoked. Mean serum estradiol levels were 196 ± 170 pg/ml (group 1), 35 ± 12 pg/ml (group 2), and 107 ± 78 pg/ml (group 3) (p = 0.004). Maximum microvascular vasodilatation (percentage increase over baseline) in response to acetylcholine was reduced in group 2 (93% ± 43%) compared with group 1 (187% ± 63%) and group 3 (142% ± 56%) (p = 0.001). The response to sodium nitroprusside also was diminished in group 2 (73% ± 27%) compared with group 1 (126% ± 45%) and group 3 (100% ± 32%) (p = 0.02). Within group 1 the acetylcholine response was higher during the midcycle phase (186% ± 31%) compared with the menstrual phase (147% ± 57%) (p < 0.05). The sodium nitroprusside response also was higher during the midcycle phase (144% ± 31%) compared with the menstrual phase (94% ± 41%) (p < 0.05) Conclusion: The results indicate that estrogens might enhance endothelium-dependent and endothelium-independent vasodilatation in the microcirculation of women.