ACTH 1-24 (Cosyntropin)
ACTH 1-24 (cosyntropin, tetracosactide) is the synthetic 24-aa N-terminal ACTH fragment retaining full biological activity. It stimulates MC2R receptors on the adrenal cortex to drive cortisol synthesis. Primarily used diagnostically in the cosyntropin stimulation test.
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Compound Profile
ACTH 1-24 (Cosyntropin)
Key Data
Research reference only
Research Focus
Preclinical data
⚠ Research & Educational Use Only. ACTH 1-24 (Cosyntropin) is a research chemical documented here for scientific education. All information references peer-reviewed literature and preclinical/clinical study data. Not for human consumption. Not medical advice. Consult a licensed researcher or healthcare professional before any laboratory use.
- Gold standard diagnostic tool: the cosyntropin (ACTH) stimulation test is the primary test for adrenal insufficiency
- Stimulates adrenocortical cortisol production within 30-60 minutes of IV/IM injection — enabling acute assessment of adrenal reserve
- Activates MC2R (ACTH receptor) on zona fasciculata cells → cAMP/PKA → StAR protein → cortisol biosynthesis
- ACTH 1-24 (Cosyntropin) is not FDA-approved for human use. FDA-approved drug: Cortrosyn (cosyntropin injection, Amphastar Pharmaceuticals). Available generically. Tetracosactide depot (Synacthen Depot) available in some European and Canadian markets.
Research At a Glance
- Gold standard diagnostic tool: the cosyntropin (ACTH) stimulation test is the primary test for adrenal insufficiency
- Stimulates adrenocortical cortisol production within 30-60 minutes of IV/IM injection — enabling acute assessment of adrenal reserve
- Activates MC2R (ACTH receptor) on zona fasciculata cells → cAMP/PKA → StAR protein → cortisol biosynthesis
- Also stimulates mineralocorticoid (aldosterone) from zona glomerulosa — useful for primary aldosteronism research
In Plain English
Simple summaryACTH 1-24 (cosyntropin, tetracosactide) is a synthetic 24-amino acid fragment of the body's adrenocorticotropic hormone -- the pituitary peptide that tells the adrenal glands to produce cortisol, aldosterone, and adrenal androgens. The full ACTH is 39 amino acids, but the first 24 are all that's needed for full biological activity at the adrenal cortex. Cosyntropin is used diagnostically in the Synacthen/Cortrosyn stimulation test -- the gold standard test for adrenal insufficiency (Addison's disease). You give a dose, then measure cortisol 30-60 minutes later: a normal rise confirms the adrenal gland can respond; a blunted or absent rise indicates adrenal insufficiency. It's an FDA-approved diagnostic tool that's been in clinical use since the 1960s.
- Gold standard diagnostic tool: the cosyntropin (ACTH) stimulation test is the primary test for adrenal insufficiency
- Stimulates adrenocortical cortisol production within 30-60 minutes of IV/IM injection — enabling acute assessment of adrenal reserve
- Activates MC2R (ACTH receptor) on zona fasciculata cells → cAMP/PKA → StAR protein → cortisol biosynthesis
The full scientific detail, mechanisms, citations, and dosing data, follows below.
What is ACTH 1-24 (Cosyntropin)?
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ACTH 1-24 (cosyntropin, tetracosactide) is the synthetic 24-amino acid N-terminal fragment of the 39-amino acid native adrenocorticotropic hormone (ACTH, corticotropin). It retains full biological potency equivalent to the entire ACTH molecule because the full receptor-binding domain and biological activity reside in the first 24 amino acids. The C-terminal residues 25-39 appear to modulate immunogenicity and pharmacokinetics but not bioactivity.
ACTH is normally produced by corticotroph cells of the anterior pituitary gland in response to CRF (corticotropin-releasing factor) from the hypothalamus and is the effector arm of the HPA (hypothalamic-pituitary-adrenal) stress axis.
**Mechanism of action:** ACTH binds to MC2R (melanocortin 2 receptor), a Gs-coupled GPCR expressed primarily on adrenocortical cells (particularly zona fasciculata and zona reticularis). Receptor activation: 1. cAMP → PKA activation 2. Phosphorylation of StAR protein (steroidogenic acute regulatory protein) → cholesterol translocation from outer to inner mitochondrial membrane 3. CYP11A1 (cholesterol side chain cleavage) → pregnenolone 4. Sequential enzymatic steps → cortisol (and, to a lesser extent, DHEA) 5. PKA also activates the transcription of CYP genes needed for sustained cortisol synthesis
The cortisol response to ACTH injection occurs within 5-10 minutes (StAR-mediated) with a peak at 30-60 minutes (new enzyme synthesis).
**Diagnostic gold standard — ACTH stimulation test:** The cosyntropin stimulation test is the most widely used test for adrenal insufficiency. By injecting 250 mcg cosyntropin IV or IM and measuring serum cortisol at 30 and 60 minutes, clinicians can determine whether the adrenal cortex can produce cortisol when maximally stimulated. A cortisol peak <18 mcg/dL suggests adrenal insufficiency (primary, secondary, or tertiary depending on context).
**ACTH therapy for infantile spasms:** The synthetic ACTH depot formulation (Synacthen/tetracosactide depot) is used for infantile spasms (West syndrome), an epilepsy syndrome of infancy. The mechanism here is distinct from cortisol stimulation — ACTH likely acts directly in the brain via MC receptors (including MC3R and MC5R) to suppress the excessive corticotropin-releasing hormone that drives the spasms.
By the Numbers
Key Research Benefits
Documented effects observed in preclinical and clinical studies on ACTH 1-24 (Cosyntropin). See all Immune System peptides for comparison.
Side Effects & Risks
Adverse effects reported in the research literature. All data sourced from preclinical and clinical study reports. View all peptides' side effects →
Dosing Data from the Literature
Doses referenced below are sourced from published preclinical and clinical studies. Use the peptide dose calculator to convert these values to injection volume.
ACTH stimulation test protocol (diagnostic):
Standard dose: 250 mcg (high-dose test) IV or IM Low-dose test: 1 mcg IV (more sensitive for partial adrenal insufficiency) Cortisol measurement: at 0, 30, and 60 minutes Normal response: Peak cortisol ≥18 mcg/dL (≥500 nmol/L) at 30-60 minutes
Synacthen Depot (for anti-inflammatory use in infantile spasms): 0.5-1 mg IM every 12-24 hours × 4-6 weeks (ACTH treatment for infantile spasms — "ACTH therapy")
Administration in Research Settings
Standard reconstitution and administration methodology for laboratory research use.
IV or IM injection for diagnostic testing. Cosyntropin (Cortrosyn) is provided as lyophilized powder for reconstitution with 0.9% NaCl. For diagnostic purposes, administer in the morning when cortisol levels are at their natural peak (8-9 AM).
What the research doesn't show
The cosyntropin stimulation test is reliable for diagnosing primary adrenal insufficiency but can miss early secondary adrenal insufficiency -- if the pituitary has recently stopped producing ACTH, the adrenal gland may not yet have atrophied and can still respond to the cosyntropin challenge. A normal Synacthen test doesn't rule out recent-onset secondary adrenal insufficiency, which is why clinical context matters.
Medical Expert Videos
Physicians, researchers, and pharmacologists explain ACTH 1-24 (Cosyntropin), covering mechanisms of action, clinical context, and study findings.
Videos sourced from YouTube search. KnowYourPeptide does not endorse any individual creator. For research education only.
The Bottom Line
ACTH 1-24 (Cosyntropin) has a growing body of preclinical evidence and a well-characterised safety profile in research settings. The most-studied application is: gold standard diagnostic tool: the cosyntropin (acth) stimulation test is the primary test for adrenal insufficiency.
The most commonly reported side effect in research subjects is hypersensitivity and anaphylaxis risk with the depot formulation (synacthen depot). It is a research chemical, not approved for human use.
Frequently Asked Questions
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Quick Reference
How It Compares
Full 39-amino acid ACTH (corticotropin) has the same adrenal-stimulating activity but is less commonly used diagnostically because it's more expensive and no more informative. Metyrapone is another HPA axis test that works differently (blocking cortisol synthesis to assess pituitary ACTH reserve). Cosyntropin is used when you suspect primary adrenal insufficiency; metyrapone is used when secondary (pituitary) failure is suspected.
Compare ACTH 1-24 (Cosyntropin) side-by-sideResearch Use Only
This information is for educational research purposes only. This is not medical advice. Consult a qualified healthcare professional.