Functioning hypersecretory PAs include prolactin (PRL)-secreting lactotroph adenomas (PRL-PAs), which represent up to 60% of all PAs, growth hormone (GH)-secreting somatotroph adenomas (GH-PAs) (8 to 16%), adrenocorticotropic hormone (ACTH)-secreting corticotroph adenomas (ACTH-PAs) (2 to 6%), and thyroid stimulating hormone (TSH)-secreting adenomas (TSH-PAs) (less than 1%) [4,5]. The gene discussed is GH1; the disease is adenoma.