Association Between the Levothyroxine Therapy and the Levels of Anti–Thyroid Antibodies in Women with Hypothyroidism Due to Hashimoto’s Thyroiditis—Narrative Review

Hashimoto’s thyroiditis (HT) is one of the most common autoimmune disorders with a complex etiology and pathogenesis, representing a significant challenge for medicine. Current pharmacological management of HT focuses on the treatment of hypothyroidism rather than addressing the underlying cause. Available scientific evidence provides limited and inconsistent data regarding the association between levothyroxine (L–T4), its dosage, and the levels of antibodies against thyroid peroxidase (anti–TPO) and thyroglobulin (anti–TG) in women with HT. Therefore, the aim of the study was to summarize current findings in this field. This narrative review was conducted using elements of the PRISMA 2020 guidelines. Literature analysis was performed using EMBASE, SCOPUS, and PUBMED databases. Articles published within the last 20 years were included. The search terms included “Hashimoto’s thyroiditis”, “Hashimoto’s disease”, “levothyroxine”, “L–thyroxine”, “anti–TPO”, “anti–TG”, “anti–thyroid antibodies”. Furthermore, to obtain a comprehensive overview of the available knowledge, the search terms were combined with “inflammation,” “treatment,” and “pregnancy”. Treatment with levothyroxine may potentially lead to a decrease in the levels of thyroid antibodies, primarily anti–TPO, in hypothyroid women with HT. Nevertheless, the direct effect of L–T4 on anti–thyroid antibody levels remains inconclusive and varies among individuals. Treatment with L–T4 in hypothyroid women with HT was also associated with improved fertility and pregnancy outcomes. The findings summarized in this review may contribute to systematizing current knowledge regarding L–T4 therapy in women with HT and its potential benefits related to fertility. Further clinical studies are required, particularly those addressing the immunological mechanisms of levothyroxine action, which may improve therapeutic precision in HT.