Objective: To assess the effects of short-term transdermal E2 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 E2 (100 microg/d) or placebo on days 1 and 4 of a 1-week treatment regimen.
Main outcome measure(s): Serum concentrations of E2 and plasma concentrations of NO stable oxidation products were assessed on day 1, 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 E2 group (40.08+/-15.42 micromol/L, 38.05+/-18.82 micromol/L, and 42.03+/-16.81 micromol/L on days 2, 3, and 6, respectively) compared with both baseline levels (23.07+/-5.79 micromol/L) and the placebo group (23.51+/-4.06 micromol/L, 21.64+/-4.72 micromol/L, and 21.81+/-4.46 micromol/L on days 2, 3, and 6, respectively).
Conclusion(s): During a 1-week treatment regimen with transdermal E2, 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.