Growth Hormone (GH1, somatotropin) is a peptide hormone secreted by the pituitary gland that has anabolic functions in development to stimulate cell reproduction, regeneration and growth. Antibodies to GH1 and other hormones (prolactin, thyroid stimulating hormone) can help classify pituitary tumors, as roughly 15-20% of pituitary adenomas produce growth hormone. In immunohistochemistry of normal tissue, GH is positive in the cytoplasm of anterior pituitary gland cells and the placenta. References: PLoS One. 2017 Jul 10;12(7):e0180039, PMID: 28692683; Front Endocrinol (Lausanne). 2015 Jun 12;6:97, PMID: 26124750; Neurosurg Focus. 2010 Oct;29(4):E2, PMID: 20887127; ISRN Endocrinol. 2013;2013:723432, PMID: 23401791; Arch Pathol Lab Med. 2017 Jan;141(1):104-112, PMID: 27227698