# ACTH (Corticotropin) > The pituitary’s command to the adrenal gland — a 39-amino-acid hormone that drives cortisol release; its 1–24 fragment is the standard test of adrenal function. - Also known as: Adrenocorticotropic hormone, Corticotropin, Acthar, Cosyntropin (1–24 analog), Tetracosactide - Class: Peptide Hormones - FDA approved: Yes - Canonical page: https://americanpeptide.com/catalog/acth ## Overview ACTH is a 39-amino-acid hormone released by the anterior pituitary that tells the adrenal cortex to make cortisol — the central relay of the body’s stress (HPA) axis. Clinically it appears in two forms: the full-length hormone as a long-acting gel (Acthar) used in select inflammatory and seizure conditions, and the synthetic 1–24 fragment cosyntropin (tetracosactide), which carries all the receptor activity and is the standard agent for testing adrenal reserve. ACTH is the middle link in the hypothalamic–pituitary–adrenal axis: the hypothalamus releases CRH, the pituitary responds with ACTH, and ACTH drives the adrenal cortex to secrete cortisol, which then feeds back to shut the loop. It is cleaved from a larger precursor, proopiomelanocortin (POMC), the same parent that yields melanocyte-stimulating hormone — which is why high ACTH states can darken the skin. Only the first 24 of its 39 residues are needed for full biological activity, and that fact is the basis of its main diagnostic use. Cosyntropin (synthetic ACTH 1–24) is given in the "ACTH stimulation test": a healthy adrenal gland responds with a brisk rise in cortisol, whereas a blunted response reveals adrenal insufficiency. The trimmed fragment is cheaper, fully active, and less immunogenic than the whole hormone. The full-length hormone has a separate, more debated life as a therapeutic. Long-acting corticotropin gel (Acthar) is used in conditions such as infantile spasms and certain flares of autoimmune disease, on the rationale that it does more than simply raise cortisol — including direct melanocortin-receptor effects. Its high cost relative to conventional steroids has made it a recurring subject of pricing scrutiny, another instance where the economics around a hormone are as notable as its biology. ## Mechanism Agonist at the melanocortin-2 receptor (MC2R) on adrenocortical cells, raising cAMP and stimulating steroidogenesis — chiefly cortisol — from the adrenal cortex. The biologically essential activity resides in the N-terminal 1–24 residues. ## Chemistry | Property | Value | | --- | --- | | Molecular weight | 4541.1 Da | | CAS number | 9002-60-2 | ## Sequence ``` SYSMEHFRWGKPVGKKRRPVKVYPNGAEDESAEAFPLEF (human 1–39) ``` ## Research areas Studied in: Adrenal insufficiency, HPA axis, Infantile spasms, Peptide hormones. Guides on this site: - [Peptide Hormone Synthesis](https://americanpeptide.com/research-areas/peptide-hormones): How hormone sequences are turned into pure, stable, manufacturable synthetic drugs. ## Key research - Adrenal function testing — cosyntropin (ACTH 1–24) is the standard stimulus in the ACTH stimulation test for adrenal insufficiency. - HPA axis — the pituitary signal that drives adrenal cortisol output; central to stress physiology and its feedback regulation. - Infantile spasms — corticotropin gel is an established treatment for this severe infantile epilepsy. - Structure–function — biological activity lives in the N-terminal 1–24 residues, the basis of the synthetic diagnostic fragment. - POMC family — cleaved from the same precursor as MSH, explaining the skin hyperpigmentation of ACTH excess. ## Storage, handling & synthesis **Synthesis.** A 39-residue hormone whose full biological activity lives in the N-terminal 1–24 segment — so the synthetic agent cosyntropin (tetracosactide) is simply that 24-mer. Truncating to the essential pharmacophore makes it markedly shorter and cheaper to build by solid-phase synthesis, avoids the difficult C-terminal residues, and lowers immunogenicity versus the whole hormone. A textbook "synthesize only the part that matters" decision in peptide drug design. ## FAQs ### What does ACTH do? ACTH (corticotropin) is a pituitary hormone that signals the adrenal cortex to release cortisol. It is the pituitary-to-adrenal step of the body’s stress (HPA) axis. ### What is cosyntropin? Cosyntropin (tetracosactide) is the synthetic first 24 amino acids of ACTH — the portion that carries all the activity. It is used in the ACTH stimulation test to assess whether the adrenal glands respond normally. ### Why is corticotropin gel controversial? The long-acting full-length hormone (Acthar) is used in conditions like infantile spasms and some autoimmune flares, but its very high cost relative to conventional corticosteroids has made it a frequent subject of pricing scrutiny. ### Is this medical advice? No — this is a research and educational reference, not dosing guidance. ## Latest research Recent trials and publications mentioning Adrenocorticotropic hormone, pulled automatically from ClinicalTrials.gov and PubMed (unfiltered search results, refreshed daily). ### Recent trials - [Prevention of West Syndrome With Low-dose Adrenocorticotropin Hormone (ACTH)](https://clinicaltrials.gov/study/NCT01367964) — TERMINATED · NA · NCT01367964 - [Pelvic Pain in Women With Endometriosis](https://clinicaltrials.gov/study/NCT00073801) — COMPLETED · NCT00073801 - [Use of Acthar in Rheumatoid Arthritis (RA) Related Flares](https://clinicaltrials.gov/study/NCT02541955) — COMPLETED · PHASE4 · NCT02541955 - [Desmopressin Stimulation Test Performance in ACTH-Dependent Cushing Syndrome](https://clinicaltrials.gov/study/NCT06635629) — RECRUITING · PHASE2 · NCT06635629 - [Adrenocorticotropic Axis and Neuropathic Pain](https://clinicaltrials.gov/study/NCT01543425) — COMPLETED · NCT01543425 - [Development and Evaluation of a Self-Management Model for Cancer Rehabilitation](https://clinicaltrials.gov/study/NCT06674499) — COMPLETED · NA · NCT06674499 --- Source: AmericanPeptide.com — https://americanpeptide.com/catalog/acth Data license: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Attribution: AmericanPeptide.com. Research reference only — computational and educational content, not medical advice.