Increased P450 aromatase levels in post-menopausal women after acute ischemic stroke

Abstract Background: Sex differences in stroke have been attributed to the neuroprotective effects of estrogen, yet most clinical trials of estrogen supplementation for stroke prevention have failed. The contribution of sex hormones to stroke outcome remains a subject of debate. Aromatization of testosterone to estradiol in neural tissue leads to sexual differentiation. Emerging data suggests aromatase activity increases in response to brain injury, and increased aromatase expression is seen in the ischemic penumbra in animal models. The objective of this study was to examine the levels of endogenous sex steroids after acute ischemic stroke and determine if levels of sex steroids were associated with acute stroke outcomes. Methods: Peripheral blood from ischemic stroke patients and controls was collected under an approved IRB within 24 hours of symptom onset. 17-β estradiol, testosterone and aromatase levels were measured in the serum of both men and women using ELISA. Hormone levels were compared in men vs. women in stroke and control groups and correlated with outcomes (NIHSS and change in the modified Rankin Scale (mRS), defined as difference of premorbid and discharge mRS) using multivariate regression. Results: We found no significant difference in estradiol levels 24 hours after stroke in men (p=0.86) or women (p=0.10). In men, testosterone significantly decreased after stroke as compared with controls (1.83±0.12 vs 2.86±0.65, p=0.01). Aromatase levels were significantly increased in women after stroke as compared with controls (2.27±0.22 vs 0.97±0.22, p=0.002), but not in men (p=0.84). Estradiol levels positively correlated with change in mRS in both women (r=0.38, p=0.02) and men (r=0.3, p=0.04).Conclusions: Estradiol levels correlated with functional outcomes (change in mRS) in both men and women, at least in the acute phase (24 hours) of stroke. However, no significant difference in estradiol levels is seen 24 hours post stroke in men or women. Testosterone levels decrease at 24 hours after stroke in men. As seen in animal models, aromatase levels increase after acute ischemic stroke, but this was only true for women. These indicate an active aromatization process in post-menopausal women after acute ischemic stroke.