CTLA4 and hypothyroidism: Frequency of frank hypothyroidism is estimated to be 6.6% with ICPis, whereas the reported incidence of hyperthyroidism is lower than that of hypothyroidism (3.2% of patients treated with anti-PD-1, 0.6% with anti-PD-L1 and 1.7% with anti-CTLA-4) [6,9].