Medical Test: What Patients Need to Know
The CRH stimulation test measures how your body responds to corticotropin releasing hormone by checking hormone levels in your blood.
{"CRH is a hormone from the hypothalamus that controls cortisol production","This test helps diagnose the cause of abnormal cortisol levels","Blood samples are taken before and after CRH injection","It can distinguish between pituitary and non-pituitary causes of Cushing's syndrome"}
Key facts at a glance
- LOINC
- 11213-6
- Short code
- CRH
- Synonyms
- ACTH RH SerPl-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or EDTA plasma tube
- Units
- N/A
- Ref low
- 10
- Ref high
- 60
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Immunoassay (Chemiluminescence, ELISA, or Radioimmunoassay)
- CPT
- 82488
- SNOMED
- 414197004
- Specimen volume
- 1-2 mL serum or plasma
- Stability
- Separate serum/plasma within 30-60 minutes of collection. Store at 2-8°C if analyzed within 24 hours; otherwise freeze at -20°C or -70°C. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 50
- Lipemia max
- 300
- Icterus max
- 20
- TAT
- 24–72 hours
- Order
- routine
This test helps your doctor learn important information about your health by examining a sample or taking specific measurements, so a condition can be identified, monitored, or ruled out as part of your overall care.
The Corticotropin Releasing Hormone (CRH) stimulation test is a blood test that evaluates how your hypothalamus-pituitary-adrenal (HPA) axis works. CRH is a hormone produced by the hypothalamus that signals your pituitary gland to release ACTH, which then stimulates your adrenal glands to produce cortisol. This test measures your body's response to synthetic CRH by tracking both ACTH and cortisol levels.
The test is usually performed by a trained health care professional in a clinic, hospital, or laboratory. The exact steps depend on the type of sample or measurement needed, and the procedure typically takes only a few minutes to complete.
A healthcare provider will insert an intravenous (IV) line into your arm. Multiple blood samples are taken—typically at baseline (before CRH), and then at 15, 30, 60, and 90 or 120 minutes after synthetic CRH is injected through the IV. Each sample is used to measure ACTH and cortisol levels. The entire procedure usually takes about 2 hours.
Follow any specific instructions from your doctor before the test. You may be asked to avoid eating or drinking for several hours, stop taking certain medications, or wear comfortable clothing. Tell your provider about all medicines, vitamins, and supplements you take, and mention any allergies or bleeding problems you have.
Fast overnight (usually 8-12 hours) before the test. Inform your doctor about all medications you are taking, as certain drugs (like steroids, antidepressants, or hormonal medications) may affect results and may need to be paused. Wear comfortable clothing with sleeves that can be easily rolled up. Your doctor will provide specific instructions based on your situation.
Most tests are safe and cause little or no discomfort. Some may involve slight pain, bruising, or a small amount of bleeding where a needle is inserted. Serious complications are rare, but contact your doctor if you develop unusual symptoms such as fever, swelling, or bleeding that does not stop.
The risks are minimal and similar to routine blood tests. You may experience mild pain or bruising at the injection site. Some people may feel flushed, lightheaded, or have a rapid heartbeat after the CRH injection, but these effects are usually temporary and subside quickly.
Reference range
Reference range varies by laboratory and assay method; typically 10-60 pg/mL (8-9 AM collection). Consult laboratory-specific reference intervals.N/A
Specimen collection preferably in the morning (8-9 AM) when CRH levels are at peak. Patient should be at rest for 30 minutes prior to collection. No fasting required, but avoid strenuous exercise before testing. Inform physician of current medications as some drugs affect CRH and cortisol levels.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The CRH test is primarily used to diagnose and differentiate causes of Cushing's syndrome. In pituitary Cushing's disease (a tumor in the pituitary gland), ACTH and cortisol levels typically rise significantly after CRH injection. In ectopic ACTH production (tumors outside the pituitary) or adrenal tumors, there is usually little to no response. The test also helps assess adrenal insufficiency and evaluate HPA axis function.
Frequently asked questions
Why do I need a CRH test?
How long does it take to get results?
What happens after the test?
Can I eat or drink during the test?
Sources
- 1
- 2
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 10, 2026. · Read our editorial policy