What thyroid disorders are associated with the use of ICPIs? How are they differentiated, and how are they managed?
A recent study reported that approximately 30% of patients on ICPIs had new-onset of thyroid function abnormalities, and an additional 70% with preexisting thyroid disorders had exacerbations appear on laboratory testing at a median time point of 33 to 46 days after starting ICPI treatment. Because of variation in the definitions of hypothyroidism, hyperthyroidism, and thyrotoxicosis, it can be hard to delineate the true incidence of these conditions in clinical trials and practice. A recent review found a 5.6% incidence of ipilimumab-related hypothyroidism and a 3.2% incidence of thyroiditis. With PD-1 inhibitors, the rates of hypothyroidism and hyperthyroidism were 5.9% and 3.3%, respectively, and with PD-L1 inhibitors the hypothyroidism incidence was 4.3%. The overall incidence of ICPI-related thyroid disease with combination therapy jumps to 13.9% for hypothyroidism, 8% for hyperthyroidism and 16.9% for other thyroid disorders, including destructive thyroiditis.