<h4>Objective</h4>To evaluate a case of pembrolizumab-induced hypoparathyroidism leading to hypocalcemia.<h4>Methods</h4>The diagnostic tests performed included calcium and parathyroid hormone level detection and calcium-sensing receptor gene analysis.<h4>Results</h4>A 71-year-old Caucasian man was diagnosed with stage IIIB adenocarcinoma of the lung and received radiation therapy but had no other exposure to radiation. This evidence concerns the gene PTH and Hypocalcemia.