Vitamin E Intake Modulates the Effect of Selenomethionine on Sexual Function and Depressive Symptoms in Reproductive-Age Women with Euthyroid Autoimmune Thyroiditis: A Pilot Study

Oxidative stress appears to be implicated in both the initiation and progression of autoimmune thyroiditis. Selenomethionine, which exhibits antioxidant properties, has been shown to reduce thyroid antibody titers in patients with autoimmune thyroiditis. Recent evidence suggests that vitamin E, a fat-soluble antioxidant, may protect against the development of autoimmune thyroiditis, and that its supplementation has been associated with improvements in female sexual function. The objective of the present pilot study was to determine whether vitamin E intake modulates the effects of selenomethionine on female sexual function and depressive symptoms in individuals with thyroid autoimmunity. The study enrolled three groups of reproductive-age women with euthyroid autoimmune thyroiditis, with 26 participants in each group. The groups were matched for age, thyroid peroxidase antibody titers, and TSH levels and differed according to vitamin E intake: adequate intake (group A), low intake (group B), and high intake (group C). All participants received selenomethionine supplementation (200 µg/day) for six months. Antibody titers and hormone levels were measured, and participants completed questionnaires assessing female sexual function (FSFI) and depressive symptoms (BDI-II). At baseline, no differences in biochemical outcomes were observed between the groups, except for testosterone levels. The study groups differed in sexual desire and arousal domain scores, which were higher in group A than in the other two groups. Total FSFI scores, the remaining FSFI domain scores, and BDI-II scores did not differ between groups at baseline. Across all groups, selenomethionine reduced thyroid peroxidase and thyroglobulin antibody titers and increased SPINA-GD and the ratio of free triiodothyronine to free thyroxine; however, the effects on antibody titers were most pronounced in group A. An increase in SPINA-GT and testosterone levels following selenomethionine supplementation was observed only in group A. In this group, selenomethionine also led to significant improvements in total FSFI scores and all individual domain scores. In contrast, in the remaining groups, the effects of supplementation were limited to increases in domain scores for lubrication, sexual satisfaction, and pain. A treatment-related reduction in total BDI-II scores was observed exclusively in women with adequate vitamin E intake. These findings suggest, for the first time, that dietary intake of a natural antioxidant may influence the effects of exogenous selenomethionine on sexual function and depressive symptoms in reproductive-age women with euthyroid autoimmune thyroiditis.