GH1 and pituitary gland adenoma: Pituitary adenomas can be derived from a single mutant cell of five differentiated cell types within pituitary gland: somatotropes, lactotropes, corticotropes, thyrotropes, and gonadotropes, which, respectively, secrete growth hormone (GH), prolactin (PRL), adrenocorticotrophic hormone (ACTH), thyroid-stimulating hormone (TSH), and gonadotropins (follicle-stimulating hormone (FSH) and luteinizing hormone (LH)).