Effects of short-term transdermal estradiol administration on plasma levels of nitric oxide in postmenopausal women

Objective: To assess the effects of short-term transdermal E-2 administration on nitric oxide (NO) plasma levels in postmenopausal women. Design: Randomized, placebo-controlled trial. Setting: Healthy volunteers in an academic research environment. Patient(s): Twenty-eight healthy postmenopausal women. Intervention(s): Transdermal administration of E-2 (100 mu g/d) or placebo on days 1 and 4 of a 1-week treatment regimen. Main Outcome Measure(s): Serum concentrations of E-2 and plasma concentrations of NO stable oxidation products were assessed on day I, before placement of the patch, and subsequently on days 2, 3, and 6. Result(s): The mean concentration of NO metabolites on days 2, 3, and 6 was significantly greater in the E-2 group (40.08 +/- 15.42 mu mol/L, 38.05 +/- 18.82 mu mol/L, and 42.03 +/- 16.81 mu mol/L on days 2, 3, and 6, respectively) compared with both baseline levels (23.07 +/- 5.79 mu mol/L) and the placebo group (23.51 +/- 4.06 mu mol/L, 21.64 +/- 4.72 mu mol/L, and 21.81 +/- 4.46 mu mol/L on days 2, 3, and 6, respectively). Conclusion(s): During a I-week treatment regimen with transdermal E-2, plasma levels of NO in postmenopausal women were significantly higher than baseline levels on days 2, 3, and 6. This suggests that the effect of estrogens on NO synthesis is rapid and that it is maintained with repeated administration. (C) 1998 by American Society for Reproductive Medicine.