Regarding tumor subtype, 35 studies (72%) included PAs with any hormonal secretion profile, 7 studies (14%) focused on functional PAs, including GH-secreting, ACTH, TSH, FSH/LH, and prolactinomas, while other 7 (14%) focused on non-functioning PAs (NFPA). This evidence concerns the gene PLOD1 and non-functioning pituitary adenoma.