Effects of Treatment with L-Thyroxine on Chronic Urticaria in Subjects with Autoimmune Thyroiditis: A Systematic...

Chronic urticaria (CU) is a condition characterized by recurrent wheals/angioedema lasting longer than 6 weeks. It is treated in a stepwise manner, starting with antihistamines and escalating to more advanced therapies, if needed. It is frequently associated with autoimmune thyroiditis (AT), and thyroid autoantibodies and thyroid-stimulating hormone (TSH) may contribute to the severity of symptoms, though the exact pathogenesis remains unclear. We performed a systematic search on Scopus and Pubmed databases, finding nine studies published between 1989 and 2018. Five studies were therefore included in our meta-analysis, and we found that the treatment with L-thyroxine (LT4) is associated with a significant improvement in CU symptoms (sMD -2.31, 95% CI -2.98 to -1.64; p < 0.00001). However, when compared with placebo or standard care, LT4 did not demonstrate superiority in terms of symptom scores. It is unclear whether it provides greater benefit in individuals with normal thyroid function or hypothyroidism, or whether it is more effective when used as suppressive or replacement therapy. Therefore, evidence for LT4 treatment improving urticaria is conflicting, with uncertain benefit prompting further evaluation and in-depth study of the molecular mechanisms and markers linking CU and AT.