They are categorised by lineage‐specific transcription factors: T‐box transcription factor 1 (TPIT), corticotroph adenomas (ACTH‐secreting), steroidogenic factor‐1 (SF1), gonadotroph adenomas (FSH and LH‐secreting) and pituitary transcription factor 1 (PIT1) lineage adenomas, including somatotroph (GH‐secreting), lactotroph (PRL‐secreting), mammosomatotroph and thyrotroph tumours.2 This evidence concerns the gene POU1F1 and ACTH-producing pituitary gland adenoma.