Human growth hormone, peptide-based

Fluorenyl-based reagent 58 has been used for the attachment of mPEG of up to 40 kDa to proteins by means of urethane bond formation (Scheme 3.11). The fluorenyl moiety releases the native unmodified protein at a slow controlled rate by hydrolysis reaction, as is shown in Equation 3.29 [216]. Reagent 58 has been used in the reversible PEGylation of exendine-4 [216], human growth hormone, interferon a2 [217], enkephalin [218], atrial natriuretic peptide [219] and insulin [220]. 

A vast number of hormones and neurotransmitters are synthesized from simple structural units including chains of amino acids. Among the amino acid based hormones are comparatively large protein molecules such as prolactin, growth hormone and insulin, and shorter chains of amino acids which may form peptide hormones, such as oxytocin and vasopressin. Protein based hormones are essential for metabolism, growth and some components of reproduction. However, evidence for specific influences of these compounds on human behavior is limited. 

Increased milk production. Much controversy exists over providing cows with supplemental bovine somatotropin (BST), also called growth hormone, a hormone that increases metabolism and milk production in dairy cows. Tbe controversy centers on human consumption of the hormone. However, BST is a peptide hormone, so it is hydrolyzed in the digestive tract and is not absorbed directly into the human bloodstream (Section 24.2). Furthermore, aU milk must contain some of this hormone, because the cow cannot produce milk without it. A more soundly based concern about BST supplementation in dairy cows is that the cows given extra BST often develop mastitis, an inflammation of the udder caused by bacterial infection. Mastitis is frequently treated with high doses of antibiotics, and some of these antibiotics could end up in tbe mUk, causing problems for people with certain food sensitivity. 

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