POMC and adenoma: Thus, transcriptomically, PA appeared to segregate and cluster according to the driving transcription factor responsible for terminal cytodifferentation of the pituitary gland: NR5A1 in the case of gonadotrophinomas, null cell and silent adenomas; TBX19 in the case of clinically manifest ACTH-adenomas; and POU1F1 in clinically manifest GH, PRL and TSH adenomas, indicating potentially, three divergent origin of the PA (Fig. 1).