In hypophysitis, idiopathic/primary forms show HLA associations and candidate pituitary autoantigens, whereas ICI-induced hypophysitis highlights a live controversy: is toxicity driven by direct anti-CTLA-4 binding to pituitary cells or by host immunogenetic predisposition (specific HLA haplotypes and immune-gene variation) that primes the axis for injury under checkpoint blockade? This evidence concerns the gene CTLA4 and hypophysitis.