CD274 and primary hypophysitis: In this review, we will focus on selected topics that highlight the impact of the immune microenvironment on pituitary gland function by describing animal models of autoimmune hypophysitis, IIH, and the role of the immune microenvironment in pituitary neuroendocrine tumors (PitNETs), with programmed cell death ligand 1 (PDL-1) as a biomarker.