Editing Adrenocorticotropic hormone (section)

== Function ==
ACTH stimulates secretion of [[Glucocorticoid|glucocorticoid steroid hormones]] from adrenal cortex cells, especially in the [[zona fasciculata]] of the adrenal glands. ACTH acts by binding to cell surface [[ACTH receptor]]s, which are located primarily on adrenocortical cells of the [[adrenal cortex]]. The ACTH receptor is a seven-membrane-spanning [[G protein-coupled receptor]].<ref name="pmid8305507">{{cite journal | vauthors = Raikhinstein M, Zohar M, Hanukoglu I | title = cDNA cloning and sequence analysis of the bovine adrenocorticotropic hormone (ACTH) receptor | journal = Biochimica et Biophysica Acta (BBA) - Molecular Cell Research | volume = 1220 | issue = 3 | pages = 329–32 | date = February 1994 | pmid = 8305507 | doi = 10.1016/0167-4889(94)90157-0 | url = https://zenodo.org/record/890717 | access-date = June 28, 2019 | archive-date = September 13, 2017 | archive-url = https://web.archive.org/web/20170913183307/https://zenodo.org/record/890717 | url-status = live }}</ref> Upon ligand binding, the receptor undergoes conformation changes that stimulate the enzyme [[adenylyl cyclase]], which leads to an increase in intracellular [[Cyclic adenosine monophosphate|cAMP]]<ref name="pmid2173715">{{cite journal | vauthors = Hanukoglu I, Feuchtwanger R, Hanukoglu A | title = Mechanism of corticotropin and cAMP induction of mitochondrial cytochrome P450 system enzymes in adrenal cortex cells | journal = The Journal of Biological Chemistry | volume = 265 | issue = 33 | pages = 20602–8 | date = November 1990 | pmid = 2173715 | doi = 10.1016/S0021-9258(17)30545-8 | url = http://www.jbc.org/content/265/33/20602.full.pdf | doi-access = free | access-date = July 24, 2012 | archive-date = September 16, 2012 | archive-url = https://web.archive.org/web/20120916170728/http://www.jbc.org/content/265/33/20602.full.pdf | url-status = live }}</ref> and subsequent activation of [[protein kinase A]].

ACTH influences steroid hormone secretion by both rapid short-term mechanisms that take place within minutes and slower long-term actions. The rapid actions of ACTH include stimulation of cholesterol delivery to the mitochondria where the [[P450scc]] enzyme is located. P450scc catalyzes the first step of steroidogenesis that is cleavage of the side-chain of cholesterol. 
ACTH also stimulates [[lipoprotein]] uptake into cortical cells. This increases the [[bioavailability]] of [[cholesterol]] in the cells of the adrenal cortex.

The long term actions of ACTH include stimulation of the transcription of the genes coding for steroidogenic enzymes, especially P450scc, steroid 11β-hydroxylase, and their associated electron transfer proteins.<ref name="pmid2173715" /> This effect is observed over several hours.<ref name="pmid2173715" />

In addition to steroidogenic enzymes, ACTH also enhances transcription of mitochondrial genes that encode for subunits of mitochondrial oxidative phosphorylation systems.<ref name="pmid7504267">{{cite journal | vauthors = Raikhinstein M, Hanukoglu I | title = Mitochondrial-genome-encoded RNAs: differential regulation by corticotropin in bovine adrenocortical cells | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 90 | issue = 22 | pages = 10509–13 | date = November 1993 | pmid = 7504267 | pmc = 47806 | doi = 10.1073/pnas.90.22.10509 | bibcode = 1993PNAS...9010509R | doi-access = free }}</ref> These actions are probably necessary to supply the enhanced energy needs of adrenocortical cells stimulated by ACTH.<ref name="pmid7504267" />

[[File:Blood values sorted by mass and molar concentration.png|thumb|center|800px|[[Reference ranges for blood tests]], showing adrenocorticotropic hormone (green at left) among the hormones with smallest concentration in the blood]]