Tetracosactide
The synthetic ACTH fragment behind the standard test of adrenal function
Tetracosactide is the first 24 amino acids of ACTH, made synthetically, which is all the hormone needs to stimulate the adrenal glands. In the US, as Cortrosyn, it is the standard diagnostic test for adrenal insufficiency; outside the US a long-acting depot form treats infantile spasms.
What is it?
Adrenocorticotropic hormone (ACTH) is made by the pituitary gland and tells the adrenal glands to produce cortisol. Its activity sits in the first part of the molecule: the Cortrosyn label notes that amino acids 1 to 20 are the minimum needed for full activity, and that shortening the chain further quickly destroys it. Tetracosactide, also called cosyntropin, is a synthetic copy of the first 24 amino acids, and 0.25 mg stimulates the adrenal cortex as fully as 25 units of natural ACTH.
Its main use in the US is diagnostic. In the short stimulation test, blood cortisol is measured before an injection and exactly 30 and 60 minutes after; a weak rise points to adrenal insufficiency. Researchers have tested simpler ways to give it: a nasal spray with chitosan produced plasma cortisol at 60 minutes equivalent to the standard intravenous test, and in people on haemodialysis the test gave equivalent results during a dialysis session.
Outside the US, a long-acting depot form treats infantile spasms, a severe epilepsy of babies; in a large analysis it stopped spasms about as often as high-dose prednisolone. The Cortrosyn label warns of hypersensitivity reactions and diagnostic inaccuracies, an audit found adverse events in about 6% of tests, and tetracosactide is named on WADA's Prohibited List.
At a Glance
Every value in this table is printed from the Grey Peptides dataset, the same record the compound explorer and comparison tool read, so the three can never disagree.
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Published Research
The studies behind tetracosactide, read from their PubMed abstracts.
Depot vs prednisolone for infantile spasms
Among 126 infants in a prospective analysis embedded in the ICISS trial, spasms had stopped on days 13 to 14 in 76% on tetracosactide depot and 67% on prednisolone, not a significant difference; development scores and later epilepsy rates also did not differ significantly.
How the short Synacthen test is used
Among 363 patients tested in Queensland public hospitals in 2020, the suspected cause of adrenal insufficiency was unclear in 46% of requests, morning cortisol was checked first in only 69%, more than one in six tests could have been avoided, and 6.1% had a documented adverse event.
Cosyntropin vs vigabatrin, randomised
In an underpowered trial of 34 children with new infantile spasms, spasms and the abnormal EEG resolved by day 14 in 75% on cosyntropin injectable suspension, 11% on vigabatrin and 38% on both. Adverse events occurred in 86% overall, with no difference between arms.
No benefit for post-dural puncture headache
In 234 deliveries complicated by accidental dural puncture, headache occurred in 60% of patients given prophylactic cosyntropin and 64% of those not given it, a difference that was not significant; epidural blood patch use also did not differ.
A nasal stimulation test
Nasal tetracosactide formulated with chitosan had a bioavailability of 14.3%, and 500 µg produced plasma cortisol at 60 minutes not significantly different from the standard 250 µg intravenous test; salivary cortisol and cortisone offered a needle-free measure, and children responded like adults.
Testing during haemodialysis
In 28 patients on chronic haemodialysis, cortisol concentrations 30 and 60 minutes after standard- and low-dose Synacthen were equivalent whether the test was done before or during dialysis, so the test can be run during a session; in 10 of 56 low-dose tests cortisol peaked by 20 minutes.
Side Effects & Contraindications
Reported Side Effects
From the studies above.
Contraindications & Cautions
Warnings from the Cortrosyn label (DailyMed, effective January 30, 2025).
Legal Status
Tetracosactide is approved in the US as a diagnostic agent.
Frequently Asked Questions
?What is the cosyntropin test?
A blood test of adrenal function: cortisol is measured before an injection of cosyntropin and 30 and 60 minutes after. A weak rise suggests adrenal insufficiency.
?Is tetracosactide the same as ACTH?
It is the first 24 of ACTH's 39 amino acids, made synthetically, which carry the hormone's full activity on the adrenal glands.
?Is tetracosactide banned in sport?
Yes. WADA's Prohibited List names it under corticotrophins and their releasing factors.
References
- [fda] US FDA, Drugs@FDA (openFDA): CORTROSYN (cosyntropin), NDA 016750, original approval April 22, 1970, prescription; cosyntropin ANDA 202147. Read October 3, 2026.
- [fda-pi] FDA. Cortrosyn (cosyntropin) US prescribing information (DailyMed set 746856e9-3930-4f6a-b8e6-a03845d6dd0b, effective January 30, 2025). Read October 3, 2026.
- [clinical-trial] Osborne JP, et al. "Prednisolone or tetracosactide depot for infantile epileptic spasms syndrome? A prospective analysis of data embedded within two randomised controlled trials." Eur J Paediatr Neurol, 2023;42:110-116. PMID: 36621063.
- [pubmed] Wootton E, et al. "A retrospective review of the short Synacthen test in Queensland hospitals." Intern Med J, 2024;54(9):1515-1522. PMID: 38660891.
- [clinical-trial] Knupp KG, et al. "Comparison of Cosyntropin, Vigabatrin, and Combination Therapy in New-Onset Infantile Spasms in a Prospective Randomized Trial." J Child Neurol, 2022;37(3):186-193. PMID: 35044272.
- [pubmed] Ellis E, et al. "Prophylactic cosyntropin after unintentional dural puncture and incidence of post-dural puncture headache and epidural blood patch use: A retrospective cohort study (2019-2022)." Int J Obstet Anesth, 2024;60:104262. PMID: 39306572.
- [clinical-trial] Elder CJ, et al. "Pharmacodynamic studies of nasal tetracosactide with salivary glucocorticoids for a noninvasive Short Synacthen Test." J Clin Endocrinol Metab, 2020;105(8). PMID: 32593173.
- [clinical-trial] Nickler M, et al. "Performance of synacthen test in chronic hemodialysis patients." BMC Nephrol, 2023;24(1):330. PMID: 37936106.
Sources & Citations
Studies were read from their PubMed records; regulatory sources are listed below, read October 3, 2026.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Consult a licensed healthcare provider before making health decisions.