Studies have so far reported that hypophysitis caused by ICIs occurs more commonly in cancer patients treated with ipilimumab (anti-CTLA4), where its prevalence is of about 12%, than in cancer patients receiving anti-PD-1 (nivolumab, pembrolizumab, cemiplimab) or anti-PD-L1 (atezolizumab, avelumab, durvalumab) treatment, in whom the reported prevalence is about 0.5% [7,8,9,10,11,12,13,14,15,19]. This evidence concerns the gene CTLA4 and cancer.