Risk of Autoimmune Thyroid Dysfunction in Multiple Sclerosis Patients Treated with Alemtuzumab: A Systematic Review

This systematic review consolidates current evidence to delineate the spectrum of alemtuzumab-induced thyroid autoimmunity in patients with MS. Methods: PubMed, Embase, Web of Science, Cochrane Library and ClinicalTrials.gov were searched up to June 2025 for studies reporting thyroid outcomes following alemtuzumab in MS. Eligible designs included randomized trials and observational cohorts. Data were extracted on incidence, subtype distribution, time to onset and management. Study quality was assessed using the Newcastle–Ottawa Scale and Cochrane/ROBINS-I tools. Results: Out of 2,397 records, 11 studies met inclusion criteria, encompassing approximately 1,626 participants. AITD occurred in about one-third of treated individuals. Graves’ disease was the predominant phenotype (33–65% of cases), followed by Hashimoto’s thyroiditis and TRAb-positive hypothyroidism. Onset typically occurred 18–30 months after the first infusion, peaking around year 3. Fluctuating courses between hyper- and hypothyroidism were reported in up to 15% of cases. Most events were mild or moderate and controlled with antithyroid drugs or levothyroxine; radioiodine or thyroidectomy were rarely required. Conclusion Autoimmune thyroid dysfunction is a frequent and distinctive complication of alemtuzumab in MS. The majority of cases are manageable, but the unpredictable course warrants regular thyroid-function testing every three months for at least four years after treatment and continued long-term surveillance.