Metformin reduces autoimmune antibody levels in patients with Hashimoto's thyroiditis: A systematic review and meta-analysis

Background In the past few years, an increasing number of studies have proposed the idea of extending the therapeutic range of metformin from traditional hypoglycaemic to autoimmune diseases, and confirmed in a variety of autoimmune diseases. However, whether metformin can be used to treat Hashimoto's thyroiditis (HT), which is characterised by thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb), is unknown. Therefore, we conducted a systematic review and meta-analysis to evaluate whether metformin can reduce the levels of TPOAb and TgAb in patients with HT or subclinical hypothyroidism (SH), so as to provide a theoretical basis for metformin treatment of these diseases. Methods PubMed, Web Of Science and Embase were searched for observational studies investigating the changes of TPOAb and TgAb in patients with HT after metformin treatment. Two authors extracted data from eligible studies and classified them as HT and subclinical hypothyroidism subgroups. The calculation was then performed by weighted mean difference (WMD) combined with a fixed-effects model analysis or standard mean difference (SMD) with a random-effects model analysis, based on the measurement of the outcome. Results Metformin significantly reduced TPOAb levels and TgAb levels in patients with HT and SH, especially TPOAb (HT:p(TPOAb)= .009,p(TgAb)= .046; SH:p(TPOAb)= .034,p(TgAb)= .066). In addition, metformin also reduced the levels of thyroid stimulating hormone (TSH), homeostasis model assessment of insulin resistance (HOMA-IR) in patients with HT and SH (HT:p(TSH)= .000 andp(HOMA-IR)= .000; SH:p(TSH)= .000 andp(HOMA-IR)= .000, respectively). Conclusion Metformin significantly reduces TPOAb level and TgAb level in patients with HT and SH, especially TPOAb. This study is the first to provide a preliminary theoretical basis for the clinical application of metformin in the treatment of HT.