GH1 and pituitary gland adenoma: Pituitary adenomas are neoplasms of the adenohypophysis (anterior pituitary gland) that can cause a multitude of symptoms secondary to the hormones they secrete (functioning adenomas) or mass effect on the optic chiasma (non-functioning adenomas). Functioning adenomas can secrete prolactin, growth hormone, adrenocorticotrophic hormone (ACTH) or thyroid-stimulating hormone, with some adenomas co-secreting more than one.