Understanding Your Diagnostic Test: What It Is, How It Is Performed, and How to Prepare
A blood test that measures 17-hydroxyprogesterone levels before and after an ACTH stimulation to evaluate adrenal gland function and diagnose conditions like congenital adrenal hyperplasia.
{"This test checks how your adrenal glands respond to a hormone stimulation","It helps diagnose congenital adrenal hyperplasia (CAH) and adrenal disorders","Blood samples are taken before and 20 minutes after receiving ACTH injection","The test is usually done in the morning after fasting","Results help doctors distinguish between different adrenal gland conditions"}
Key facts at a glance
- LOINC
- 59155-2
- Short code
- 17-OHP ACTH stim 20min
- Synonyms
- 17OHP 20M p chal SerPl-sCnc
- Category
- chemistry
- Sample
- serum
- Container
- Serum Separator Tube (SST, gold top) or plain red top tube
- Units
- N/A
- Ref low
- 2
- Ref high
- 15
- Critical range
- — – 50 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Chemiluminescence Immunoassay (CLIA) or Enzyme-Linked Immunosorbent Assay (ELISA)
- CPT
- 82533
- SNOMED
- 314255001
- Specimen volume
- 1-2 mL serum minimum
- Stability
- Room temperature: 24 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 30 days. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 50
- Lipemia max
- 300
- Icterus max
- 40
- TAT
- 24–72 hours
- Order
- routine
This test is a diagnostic procedure that your healthcare provider may order to check how your body is working, look for signs of illness, confirm or rule out a suspected condition, and help guide the most appropriate treatment plan for your specific health needs.
The 17-Hydroxyprogesterone (17-OHP) challenge test is a diagnostic procedure that measures the level of 17-hydroxyprogesterone in your blood before and after an ACTH (adrenocorticotropic hormone) injection. ACTH is a hormone produced by the pituitary gland that stimulates the adrenal glands to produce cortisol and other hormones. This test evaluates how well your adrenal glands are functioning and helps identify certain disorders.
A trained member of our medical team will perform the test in a comfortable clinical setting, following careful, standardized steps to collect the sample or information needed, and most patients find the process quick, simple, and well tolerated from start to finish.
The test typically involves the following steps: First, a healthcare provider will draw a baseline blood sample to measure your initial 17-OHP level. Then, synthetic ACTH is injected into your muscle or vein. After exactly 20 minutes (and sometimes again at 60 minutes), another blood sample is drawn to measure how your adrenal glands responded to the stimulation. The entire procedure usually takes about 1-2 hours.
In many cases you can eat and drink normally and take your regular medicines, but your provider may give you specific instructions, such as fasting for a certain number of hours or temporarily avoiding certain medications, so please follow all directions you receive and ask questions if anything is unclear.
Your doctor may ask you to fast overnight before the test. Inform your doctor about all medications you are taking, as certain medications (like corticosteroids, hormones, or birth control pills) may affect the results. It's important to mention any recent illnesses or stress, as these can also influence hormone levels. The test is usually scheduled in the morning because hormone levels follow a daily rhythm.
This test is considered very safe, and serious complications are rare; you may notice minor, temporary effects such as mild discomfort, slight bruising, or brief dizziness, and you should contact your healthcare provider if you experience unusual pain, swelling, bleeding, or signs of infection afterward.
The risks are minimal and similar to routine blood tests. You may experience slight pain or bruising at the injection site. Some people might feel flushed or experience a rapid heartbeat briefly after the ACTH injection. Serious allergic reactions to ACTH are rare but possible. The amount of blood taken is small, so there is minimal risk of anemia.
Reference range
Reference range: 2-15 nmol/L at 20 minutes post-ACTH challenge; values >30 nmol/L suggest congenital adrenal hyperplasia (CAH). Normal response shows significant rise from baseline.N/A
No fasting required. Patient should rest for 30 minutes before test. Inform patient about ACTH (cosyntropin) injection procedure. Document current medications, especially corticosteroids or hormonal contraceptives that may affect results.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test is primarily used to diagnose and evaluate congenital adrenal hyperplasia (CAH), a genetic disorder affecting the adrenal glands' ability to produce cortisol. In CAH due to 21-hydroxylase deficiency, 17-OHP levels are significantly elevated and rise dramatically after ACTH stimulation. The test also helps differentiate between various forms of CAH and other adrenal disorders. It can be used to monitor treatment effectiveness in patients with CAH and to assess adrenal insufficiency. In adults, this test may help evaluate certain types of adrenal tumors or Cushing's syndrome.
Normal response shows a moderate rise in 17-OHP after ACTH stimulation. Abnormally high levels (typically above 1000 ng/dL at 20 or 60 minutes) strongly suggest classic congenital adrenal hyperplasia. Intermediate elevations may indicate non-classical CAH or other adrenal issues. Your doctor will interpret your results in context with your symptoms, physical examination, and other test results.
Frequently asked questions
Why do I need an ACTH stimulation test?
How long does the test take?
What do abnormal results mean?
Are there any side effects from the ACTH injection?
Do I need to stop my medications before the test?
Sources
- 1
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- 3
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