Alemtuzumab-Induced Autoimmune Thyroid Dysfunction.

Alemtuzumab, a humanized monoclonal antibody used as a disease-modifying treatment in relapsing-remitting multiple sclerosis (RRMS), frequently causes autoimmunity as its principal adverse effect. We describe a typical case of a young man treated with two courses of alemtuzumab presenting 18 months later with initial hyperthyroidism due to Graves' disease (GD) followed by persistent hypothyroidism. We discuss the pathophysiological role of stimulating and blocking thyrotropin receptor antibodies in the development of alemtuzumab-induced autoimmune thyroid dysfunction and clinical challenges posed by spontaneous, bidirectional switching between hyperthyroidism and hypothyroidism. Guidelines recommend monitoring thyroid function pre-treatment and every three months for four years following alemtuzumab treatment. Patient education is crucial for maintaining adherence to monitoring programs.