The Protective Effect of Exogenous 17-Estradiol against Experimentally Induced Oxidative Damage to Membrane Lipids Is Stronger in Male vs. Female Porcine Thyroids: Preliminary Results

It is well-known that thyroid diseases are more prevalent in women than in men. The contribution of sex hormones may explain such disparity. The aim of this study was to check if there are any differences between sexes concerning the effects of 17 beta-estradiol on oxidative damage to membrane lipids (lipid peroxidation) in porcine thyroid homogenates under basal conditions and in the presence of Fenton reaction (Fe2+ + H2O2 -> Fe3+ + (OH)-O-center dot + OH-) substrates. We observed that 17 beta-estradiol did not change the basal level of lipid peroxidation (measured spectrophotometrically as concentrations of malondialdehyde + 4-hydroxyalkenals) in thyroid homogenates, and no differences were found between sexes. The lipid peroxidation level in response to Fe2+ + H2O2 plus 17 beta-estradiol was lower in male thyroids. In turn, in male thyroids, 17 beta-estradiol reduced experimentally induced lipid peroxidation in as low of a concentration as 0.1 mu M, whereas in female thyroids the lowest effective concentration of 17 beta-estradiol was 10 mu M, i.e., 100 times higher than in males. In conclusion, the protective effects of exogenous 17 beta-estradiol against experimentally induced oxidative damage to membrane lipids is stronger in male than in female thyroids. Our observation suggests that female tissue is less sensitive to the protective effects of exogenous 17 beta-estradiol. This sexual dimorphism of oxidative processes in the thyroid may constitute one of the mechanisms of the different prevalence of thyroid diseases in women and in men.