POU1F1 and pituitary gland adenoma: There are three main transcription factors determining terminal differentiation of the anterior pituitary cell lineages: POU1F1, controls somatotrope, thyrotrope and lactotrope differentiation and is expressed in GH-, TSH- and PRL-secreting tumors; NR5A1, controls gonadotrope differentiation and is expressed in most clinically non-functioning pituitary adenomas (NFPA) which produce LH and/or FSH; and TBX19, which dictates corticotrope differentiation and is expressed in ACTH-producing tumors causing Cushing disease and in silent ACTH adenomas [2].