BMP4 and pituitary gland adenoma: Similarly, transcript levels of GAL (galanin), a marker for lactotrophs [28], was highly expressed in the pituitaries of TG mice, as were transcripts for BMP4 (bone-morphogenetic protein 4, a signalling molecule required for early embryonic and pituitary development [29]) and PTTG1 (pituitary tumor transforming growth factor 1, an oncogene expressed in pituitary adenomas [30], [31]).