[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Diagnostic agents](https://durgical.com/en/pharmacology/classes/diagnostic-agents/) › Tetracosactide

# Tetracosactide

## Diagnostic agents?

Diagnostic agents

Synthetic ACTH (its first 24 amino acids) used for the ACTH stimulation test: if cortisol does not rise, the adrenal glands are failing.

Updated Nov 12, 2026

Also called: cosyntropin, ACTH 1-24, tetracosactrin

## Quick facts

**Group**
[Diagnostic agents](https://durgical.com/en/pharmacology/classes/diagnostic-agents/)

**Target**
Melanocortin-2 receptor (ACTH receptor) on adrenal cortex cells

**Key effects**
Rash · Fast or slow heart rate · Raised blood pressure

**Monitor**
Serum cortisol before

**ATC**
H01AA02

No doses: the clinician sets them by the current guideline.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

◎**Melanocortin-2 receptor (ACTH receptor) on adrenal cortex cells**Tetracosactide

ⓘ The figure shows natural ACTH (its first residues) bound to MC2R with its partner protein MRAP1; tetracosactide is the first 24 amino acids of ACTH.

**Target in 3D:** Melanocortin-2 receptor (ACTH receptor) on adrenal cortex cells. PDB structure 8GY7 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/8GY7) · Drag to rotate · pinch to zoom

Tetracosactide is the first 24 amino acids of ACTH, the part that carries all of the hormone's adrenal-stimulating activity. It binds the ACTH receptor on adrenal cortex cells and makes them release cortisol within minutes. In the stimulation test, cortisol is measured before and after the injection: a healthy adrenal cortex responds with a clear rise, a failing one does not. Because the fragment is short, it is less allergenic than natural ACTH.

- Baseline cortisol is drawn
- Tetracosactide binds adrenal ACTH receptors
- A healthy adrenal cortex releases cortisol
- A low stimulated cortisol suggests adrenal insufficiency

## Indications

- Diagnostic screening for adrenocortical insufficiency (ACTH stimulation test), in adults and children [Adrenal insufficiency →](https://durgical.com/en/conditions/adrenal-insufficiency/)

## Adverse effects

### Common

- Rash
- Fast or slow heart rate
- Raised blood pressure
- Peripheral oedema

### Serious (rare, important)

- Hypersensitivity reactions, including anaphylaxis

## Contraindications

- Previous hypersensitivity to tetracosactide or its excipients

## Key interactions

**Glucocorticoids (for example hydrocortisone, prednisolone) and spironolactone**
Can falsely raise measured cortisol; usually withheld on the test day

**Oestrogen-containing medicines**
Raise cortisol-binding globulin and total cortisol; typically stopped weeks before testing

## What is monitored

- Serum cortisol before and after the injection
- Signs of an allergic reaction during and after the test
- Conditions that alter cortisol-binding globulin (cirrhosis, nephrotic syndrome), which make results less reliable

## Administration and safety

- The powder is reconstituted before injection
- Blood samples are timed exactly and labelled with the collection time
- Resuscitation equipment is ready in case of anaphylaxis

## Pregnancy and breastfeeding

Decades of case reports have not shown an increase in birth defects or miscarriage; untreated adrenal insufficiency is itself dangerous in pregnancy.

## Nursing care

- Check which steroid or oestrogen medicines the patient takes and whether they were withheld
- Draw the baseline sample before the injection
- Observe the patient for allergic reactions
- Do not delay treatment of suspected adrenal crisis to complete the test

## Pharmacokinetics

**Absorption**
Given by intravenous or intramuscular injection

**Onset and duration**
Cortisol is measured about 30 and 60 minutes after the injection

## Memory aid

TETRA-COSA: 24 (tetracosa) amino acids, 2 blood samples, 1 question: does cortisol rise?

## Test yourself

Think of the answer, then tap the question to see it.

## What is tetracosactide?

A synthetic peptide made of the first 24 amino acids of ACTH, which carry its full adrenal-stimulating activity.

## What result of the ACTH stimulation test suggests adrenal insufficiency?

A low stimulated cortisol: the adrenal cortex does not respond with a clear rise.

## Which medicines can falsely raise cortisol during the test?

Glucocorticoids and spironolactone; oestrogens raise total cortisol through cortisol-binding globulin.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/tetracosactide/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## Connections

## Related drugs 3

- [Hydrocortisone](https://durgical.com/en/pharmacology/hydrocortisone/)
- [Fludrocortisone](https://durgical.com/en/pharmacology/fludrocortisone/)
- [Metyrapone](https://durgical.com/en/pharmacology/metyrapone/)

## Related conditions 1

- [Adrenal insufficiency](https://durgical.com/en/conditions/adrenal-insufficiency/)

[← Back to the class: Diagnostic agents](https://durgical.com/en/pharmacology/classes/diagnostic-agents/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - COSYNTROPIN injection, powder, lyophilized, for solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=1342169c-e214-4f22-8363-1fd45b85d1e8) (DailyMed (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=H01AA02) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [Cryo-EM structure of ACTH-bound melanocortin-2 receptor in complex with MRAP1 and Gs protein](https://www.rcsb.org/structure/8GY7) (RCSB Protein Data Bank, 2026).

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Representative model, for educational purposes only.

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