Editing Growth hormone (section)

===Structure===
The major isoform of the human growth hormone is a protein of 191 [[amino acid]]s and a molecular weight of 22,124 [[Atomic mass unit|daltons]]. The structure includes four helices necessary for functional interaction with the GH receptor. It appears that, in structure, GH is evolutionarily homologous to prolactin and chorionic somatomammotropin. Despite marked structural similarities between growth hormone from different [[species]], only human and [[Old World monkey]] growth hormones have significant effects on the human [[growth hormone receptor]].<ref name="pmid12082127">{{cite journal | vauthors = Yi S, Bernat B, Pál G, Kossiakoff A, Li WH | title = Functional promiscuity of squirrel monkey growth hormone receptor toward both primate and nonprimate growth hormones | journal = Molecular Biology and Evolution | volume = 19 | issue = 7 | pages = 1083–92 | date = July 2002 | pmid = 12082127 | doi = 10.1093/oxfordjournals.molbev.a004166 | doi-access = free }}</ref>

Several [[molecule|molecular]] isoforms of GH exist in the pituitary gland and are released to blood. In particular, a variant of approximately 20 kDa originated by an alternative splicing is present in a rather constant 1:9 ratio,<ref name="pmid12217902">{{cite journal | vauthors = Leung KC, Howe C, Gui LY, Trout G, Veldhuis JD, Ho KK | title = Physiological and pharmacological regulation of 20-kDa growth hormone | journal = American Journal of Physiology. Endocrinology and Metabolism | volume = 283 | issue = 4 | pages = E836–43 | date = October 2002 | pmid = 12217902 | doi = 10.1152/ajpendo.00122.2002 }}</ref> while recently an additional variant of ~ 23-24 kDa has also been reported in post-exercise states at higher proportions.<ref name="pmid19003817">{{cite journal | vauthors = Kohler M, Püschel K, Sakharov D, Tonevitskiy A, Schänzer W, Thevis M | title = Detection of recombinant growth hormone in human plasma by a 2-D PAGE method | journal = Electrophoresis | volume = 29 | issue = 22 | pages = 4495–502 | date = November 2008 | pmid = 19003817 | doi = 10.1002/elps.200800221 | s2cid = 22525768 }}</ref> This variant has not been identified, but it has been suggested to coincide with a 22 kDa glycosylated variant of 23 kDa identified in the pituitary gland.<ref name="pmid19579232">{{cite journal | vauthors = Bustamante JJ, Gonzalez L, Carroll CA, Weintraub ST, Aguilar RM, Muñoz J, Martinez AO, Haro LS | title = O-Glycosylated 24 kDa human growth hormone has a mucin-like biantennary disialylated tetrasaccharide attached at Thr-60 | journal = Proteomics | volume = 9 | issue = 13 | pages = 3474–88 | date = July 2009 | pmid = 19579232 | pmc = 2904392 | doi = 10.1002/pmic.200800989 }}</ref> Furthermore, these variants circulate partially bound to a protein ([[growth hormone-binding protein]], GHBP), which is the truncated part of the [[growth hormone receptor]], and an acid-labile subunit (ALS). {{cn|date=November 2024}}