When cortisol is clearly too high and ACTH is also high, clinicians still need to know whether the ACTH is coming from the pituitary or from an ectopic source. Acthrel (corticorelin ovine triflutate) is a synthetic CRH-like peptide used in a supervised stimulation test for that differential. The everyday takeaway is that this is a specialized hospital or endocrine-clinic infusion with timed blood draws—not a home cortisol kit, and not the same test as a cosyntropin ACTH stim screen for adrenal insufficiency.
What the CRH stim test is trying to answer
MedlinePlus describes Cushing syndrome as long-term high cortisol with many possible causes. After labs confirm ACTH-dependent hypercortisolism and adrenal tumors are not the driver, the Acthrel label says the corticorelin test helps separate pituitary ACTH excess (Cushing disease) from ectopic ACTH production. In the labeled pattern, pituitary disease often shows a rise in ACTH and cortisol after the infusion, while ectopic ACTH often shows little response. UniProt lists corticotropin-releasing hormone (P06850) as the native hypothalamic peptide this diagnostic agent mimics.
No single stim test is perfect. Imaging, other dynamic tests, and sometimes inferior petrosal sinus sampling still enter the pathway when results conflict. Ask where you are in that sequence before assuming Acthrel alone will name the source.
What to expect on test day and what to report
The label describes a timed venous sampling schedule around a brief intravenous infusion, with baseline samples before the dose and follow-up samples afterward. Hypersensitivity reactions—including flushing, breathing difficulty, and orofacial swelling—are labeled risks; the product is contraindicated after prior hypersensitivity to ovine corticorelin or its excipients. Higher-than-recommended doses historically linked to more cardiovascular symptoms, which is why teams stick to the labeled weight-based plan.
Bring a full medicine list, mention prior allergic reactions to diagnostic peptides, and ask how long you will be observed after the infusion. Confirm whether you should arrive fasting per the center’s protocol and who will explain results in plain language (rise versus flat ACTH/cortisol pattern).
Questions that change what you notice next. Before scheduling, write down which prior tests already proved high cortisol and high ACTH, whether adrenal imaging was already done, and whether any ectopic tumor search has started. Ask how Acthrel differs from a cosyntropin stim test you may have heard about for adrenal failure, what happens if results are indeterminate, and whether petrosal sampling is on the contingency list. Keep the timed lab printouts; source-of-ACTH decisions often hinge on percentage rises that are hard to reconstruct from memory.
Not medical advice.
Sources
- DailyMed: Acthrel (corticorelin) prescribing information
- MedlinePlus: Cushing syndrome
- UniProt: Corticotropin-releasing hormone (P06850)
Related reading
- Cosyntropin ACTH stim tests for adrenal insufficiency
- Secretin stim tests and acid-suppressing pills
- High prolactin tests often need a retest
By The Everyday Brief. AI-assisted drafting with human editorial review. Sources fetched 2026-10-10 PT. Not medical advice.