Résumé : This paper deals with thyroid disease that can occur after treatment with alemtuzumab (humanized monoclonal anti-CD52) for relapsing–remitting multiple sclerosis (MS). The 5-year incidence of thyroid adverse events in phase 3 clinical trials is up to 40.7%. In most cases, the thyroid dysfunction is mild and easily manageable and only few serious thyroid adverse events have been reported. The need for patient education on the risk of thyroid dysfunction, as well as regular clinical and biochemical thyroid function screening is well described. However, practical clinical guidance in case of abnormal thyroid-related findings prior to or after alemtuzumab treatment is currently lacking. Therefore, a Belgian taskforce consisting of MS and thyroid experts was created in 2016, with the objective of issuing a clinical thyroid management algorithm based on available scientific evidence and personal experience with regard to alemtuzumab treatment-related thyroid adverse events.