Somatomammotropin family

Hormone Site of Secretion Chemistry Location of Gene Function Regulation of Secretin 

Growth Hormone (GH) Anterior Pituitary (Somatotroph) 191aa(22kDa) 17q22-q24 Stimulates protein synthesis in many tissues exerts protein-sparing effects stimulates production of IGFs. Primarily stimulated by GHRH and inhibited by somatostatin. 

Prolactin (PRL) Anterior Pituitary (Lactotroph) 198 aa (23 kDa) 6p22.2-q21.3 Stimulates growth and protein synthesis in breast promotes milk secretion during lactation. Primarily inhibited by PIH (dopamine) stimulated by PRF and TRH. 

Anterior pituitary hormones are classihed into three families the somatomammotropin family (GH and PRL), the glycoprotein hormones (LH, FSH, and TSH), and the opiomelanocortin family (ACTH, /i-endorphin, and related peptides). These three families appear to have evolved from three separate ancestral polypeptides homologous members of each family occur in other parts of the body. For example, human placental lactogen (hPL) is somatomammotropic, human chorionic gonadotrophin (hCG) is a glycoprotein hormone, and the brain and gut produce substances related to endorphins (enkephalins and dynorphin). 

Members of the somatomammotropin family are singlechain proteins with two or three intrachain disulhde bridges their molecular weight is about 20,000, and they 

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Structural homology in the somatomammotropin family. Diagram of basic structure of human chorionic somatomammotropin, human growth hormone, and ovine prolactin. Bars represent the peptide chains with the amino terminus at left and the carboxyl terminus at right. Shaded portions of each bar represent the areas of homology. Lines above the bars represent disulfide bridges. [Reproduced with permission from H. D. Niall,... 

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