Effect of Estrogen Replacement Therapy on Natural Killer Cell Activity in Postmenopausal Women

Objective: To evaluate the impact of menopause and estradiol substitution on natural killer cell activity.

Methods: Natural killer cell activity and antibody-dependent cellular cytotoxicity were measured in peripheral blood of 53 postmenopausal and 20 premenopausal women in an interval of 3 weeks. Postmenopausal patients were randomly assigned to receive either estradiol valerate (2 mg daily) orally (n = 18), estradiol (50 micrograms/24 h) transcutaneously (n = 18) or no substitution (n = 17), and the testing was repeated 3 weeks later.

Results: Natural killer cell activity but not antibody-dependent cellular cytotoxicity was significantly (P < 0.01) higher in unsubstituted postmenopausal compared to premenopausal subjects. Natural killer cell activity decreased both in orally and transcutaneously estradiol-treated patients (mean [S.D.] before vs. after 3 weeks; oral: 60.8 [9.2]% vs. 52.8 [8.2]% P < 0.01; transcutaneous: 61.5 [10.6]% vs. 54.3 [9.1]% P < 0.01; no substitution: 60.6 [10.6]% vs. 59.3 [8.9]% P > 0.1), whereas antibody-dependent cellular cytotoxicity showed no changes. The addition of 0.1 to 10 ng/ml estradiol to peripheral blood mononuclear cells of untreated postmenopausal women in vitro had no influence upon natural killer cell activity.

Conclusion: Postmenopausal women receiving no estrogen replacement exhibited an increased natural killer cell activity which decreased during estrogen substitution.