From the Guidelines
The ACTH stimulation test is not reliable in patients taking hydrocortisone, and it is recommended to discontinue hydrocortisone for at least 24 hours before the test to ensure accurate results. This is because exogenous hydrocortisone can suppress the body's natural cortisol production, leading to potentially false-negative results 1. The ACTH stimulation test measures the adrenal glands' response to ACTH by producing cortisol, and when a patient is taking hydrocortisone, the test cannot distinguish between the body's natural cortisol production and the medication.
Some key considerations when interpreting ACTH stimulation test results in patients taking hydrocortisone include:
- The need to hold hydrocortisone for 24 hours before assessing endogenous function 1
- The potential for false-negative results due to suppressed adrenal reserve 1
- The importance of consulting endocrinology for recovery and weaning protocols using hydrocortisone in patients with symptoms of adrenal insufficiency 1
In clinical practice, it is crucial to weigh the risks and benefits of discontinuing hydrocortisone before the ACTH stimulation test, particularly in patients who cannot safely stop the medication due to medical necessity. Alternative testing approaches, such as measuring ACTH levels or performing the test while documenting the timing and dosage of hydrocortisone administration, may be necessary in these cases 1.
From the Research
Reliability of ACTH Stimulation Test in Patients Taking Hydrocortisone
The reliability of the Adrenocorticotropic hormone (ACTH) stimulation test in patients taking hydrocortisone is a topic of interest due to the potential interference of hydrocortisone with the test results.
- The test is used to assess adrenal responsiveness, but its reliability can be affected by various factors, including the use of corticosteroids like hydrocortisone 2.
- According to a study published in 2007, hydrocortisone can interfere with the cortisol test, making it difficult to interpret the results of the ACTH stimulation test 2.
- However, another study published in 2019 suggests that the ACTH stimulation test can still be useful in diagnosing adrenal insufficiency, but clinicians should be aware of the potential pitfalls in interpreting the results, including the impact of corticosteroid therapy 3.
- A more recent study published in 2024 found that salivary cortisol response to ACTH stimulation can be a reliable alternative to serum cortisol in evaluating hypoadrenalism, which may be useful in patients taking hydrocortisone 4.
- An older study from 1976 compared the adrenocortical response to the ACTH stimulation test with the hypothalamic-pituitary-adrenocortical response to insulin-induced hypoglycaemia and found a highly significant correlation between the two tests, suggesting that the ACTH stimulation test can be reliable in detecting impaired hypothalamic-pituitary-adrenocortical function 5.
- It is also worth noting that a study from 1994 recommended that the ACTH stimulation test should not be used for patients suspected of having secondary adrenal insufficiency, as it may not provide accurate results 6.
Factors Affecting Test Reliability
Several factors can affect the reliability of the ACTH stimulation test in patients taking hydrocortisone, including:
- The dose and duration of hydrocortisone therapy
- The timing of the test in relation to hydrocortisone administration
- The type of assay used to measure cortisol levels
- The presence of other medical conditions that can affect cortisol production or metabolism 2, 3, 4.
Clinical Implications
The clinical implications of the ACTH stimulation test results in patients taking hydrocortisone should be interpreted with caution, taking into account the potential interference of hydrocortisone with the test results 2, 3.