Concerning parathyroid involvement, hypoparathyroidism (and exceptionally primary hyperparathyroidism [198]) was diagnosed despite the fact that parathyroid tissue does not hold receptors for PD-1, PD-L1, or CTLA-4, but, probably, antibodies against the calcium-sensing receptor are drug-induced [199,200,201]. Here, PDCD1 is linked to hypoparathyroidism.