Cortisol Provocation Test – Procedure & Significance
The cortisol provocation test is a diagnostic procedure used to assess adrenal gland function and the stress hormone response of the hypothalamic-pituitary-adrenal axis.
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The cortisol provocation test is a diagnostic procedure used to assess adrenal gland function and the stress hormone response of the hypothalamic-pituitary-adrenal axis.
What Is the Cortisol Provocation Test?
The cortisol provocation test is an endocrinological diagnostic procedure used to evaluate the function of the hypothalamic-pituitary-adrenal (HPA) axis. This axis regulates the secretion of cortisol, the body´s primary stress hormone. During the test, the adrenal glands are deliberately stimulated or challenged to determine whether they are capable of producing and releasing adequate amounts of cortisol in response to a trigger.
When Is the Test Used?
The cortisol provocation test is indicated when impaired cortisol production is suspected. Common indications include:
- Adrenal insufficiency (primary or secondary) – reduced or absent cortisol production
- Addison's disease – an autoimmune condition affecting the adrenal cortex
- Hypopituitarism – underfunction of the pituitary gland
- Suspected Cushing's syndrome – pathological overproduction of cortisol
- Follow-up after surgery on the pituitary gland or adrenal glands
- Long-term corticosteroid therapy with assessment of adrenal suppression
How Does the Test Work?
Several variants of the cortisol provocation test exist, depending on the clinical question being investigated:
ACTH Stimulation Test (Synacthen Test)
This is the most commonly used form. The patient receives an injection of synthetic ACTH (tetracosactide/Synacthen), a hormone normally secreted by the pituitary gland that stimulates the adrenal cortex to produce cortisol. Blood samples are taken before the injection and again at 30 and 60 minutes afterward. A normal rise in cortisol levels indicates intact adrenal function.
Insulin Tolerance Test (ITT)
In this test, a controlled drop in blood sugar (hypoglycemia) is induced by administering insulin. This serves as a strong physiological stress stimulus that provokes maximum activation of the HPA axis. The insulin tolerance test is considered the gold standard for assessing central cortisol reserve, but it requires close medical supervision throughout.
CRH Stimulation Test
Corticotropin-releasing hormone (CRH), which is normally produced by the hypothalamus, is administered to stimulate ACTH release from the pituitary gland. This test helps differentiate between primary adrenal insufficiency and secondary (pituitary) or tertiary (hypothalamic) causes.
Metyrapone Test
Metyrapone inhibits cortisol synthesis in the adrenal cortex, triggering a compensatory activation of the pituitary gland. This test is used to evaluate pituitary function and to differentiate between various forms of Cushing's syndrome.
Dexamethasone Suppression Test
Unlike stimulation tests, this test involves administering a synthetic corticosteroid (dexamethasone) that normally suppresses cortisol production. If suppression does not occur, this may indicate Cushing's syndrome. The test is performed in several variants, including low-dose overnight, two-day low-dose, and high-dose protocols.
Preparation and Procedure
The exact preparation depends on the test variant chosen. General guidance includes:
- Blood samples are typically collected in the morning between 8 and 9 a.m., as cortisol follows a circadian rhythm with a natural morning peak
- Corticosteroid medications should be discontinued before the test if medically safe to do so
- The patient may be required to fast, depending on the specific protocol
- The insulin tolerance test requires continuous medical supervision and immediate access to glucose for emergency treatment
Interpretation of Results
Test results must always be interpreted in the clinical context. General reference values (which may vary by laboratory) include:
- Normal cortisol response in the ACTH test: peak cortisol above 500 nmol/l is considered adequate in most guidelines
- Absent or blunted response: suggests primary or secondary adrenal insufficiency
- Failure to suppress in the dexamethasone test: raises suspicion for Cushing's syndrome
- All results should be interpreted by an endocrinologist
Risks and Side Effects
Most variants of the cortisol provocation test are well tolerated. Potential risks include:
- Mild allergic reactions to injected substances (rare)
- Insulin tolerance test: risk of severe hypoglycemia, seizures – therefore only performed under strict supervision
- Contraindicated in patients with coronary artery disease, epilepsy, or severe pituitary insufficiency, depending on the test variant
References
- Bornstein SR et al. – Diagnosis and Treatment of Primary Adrenal Insufficiency: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology and Metabolism, 2016.
- Fleseriu M et al. – Consensus on Diagnosis and Management of Cushing's Disease: A Guideline Update. Lancet Diabetes and Endocrinology, 2021.
- World Health Organization (WHO) – Endocrine Disorders: Adrenal Insufficiency Overview. WHO Technical Report, 2020.
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