PDCD1 and hypothyroidism: Like all immunotherapies, ICIs like ipilimumab and tremelimumab, which target cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), and nivolumab and pembrolizumab, which target programmed cell death protein 1 (PD-1), are associated with adverse effects, including hypothyroidism, Graves’ disease, and painless thyroiditis (2–4).