From the Guidelines
Before long-term withdrawal of steroids, a short Synacthen test is recommended to assess adrenal function, as it helps determine if the hypothalamic-pituitary-adrenal (HPA) axis has recovered sufficiently to produce adequate cortisol independently. This is particularly important for patients who have been on steroids for more than 1 month at a dose equivalent to prednisolone ≥ 5 mg, as their adrenal glands may have become suppressed due to negative feedback from exogenous steroids, potentially leading to adrenal crisis if steroids are withdrawn too quickly 1.
Key Considerations
- The short Synacthen test involves measuring baseline cortisol levels, administering 250 micrograms of synthetic ACTH (Synacthen/cosyntropin) intravenously or intramuscularly, then measuring cortisol levels again after 30 and 60 minutes.
- A normal response (cortisol level >500-550 nmol/L or >18-20 μg/dL) indicates adequate adrenal function and suggests steroids can be safely withdrawn.
- If the test shows inadequate response, steroid withdrawal should proceed more cautiously with slower tapering to allow the HPA axis more time to recover.
Rationale
- Studies have shown that a daily glucocorticoid dose equivalent to prednisolone ≥ 5 mg, for longer than 1 month, represents an adrenal suppressive dose in a proportion of adults 1.
- The data from case series of short Synacthen tests performed in populations receiving therapeutic corticosteroid treatment of between 5 mg and 20 mg prednisolone daily, report a variable number of patients (approximately one third to a half) not achieving the target cortisol concentration when 5 mg or more of prednisolone was administered 1.
- Given the risks of an inadequate glucocorticoid response, individualised glucocorticoid supplementation in addition to ongoing treatment during the peri-operative period (and by extension whenever patients are subjected to any physiological stress), is supported in this group of patients 1.
From the Research
Assessment of Hypothalamic-Pituitary-Adrenal Axis Before Long-Term Withdrawal of Steroids
- The short synacthen test (SST) is a reliable method for assessing the hypothalamic-pituitary-adrenal (HPA) axis in patients on long-term corticosteroid therapy 2.
- The SST can be used as an initial assessment of the HPA axis, and the insulin tolerance test (ITT) can be used for those who fail the SST 2.
- A study found that the SST is a suitable substitute for the ITT in assessing the HPA axis, with a 30-minute cortisol value > 600 nmol/l as a cut-off 3.
- Another study suggested that baseline serum cortisol, salivary cortisone, and salivary cortisol can be used to predict HPA axis recovery, reducing the need for short synacthen tests by 50%, 46%, and 37%, respectively 4.
Importance of Short Synacthen Test Before Withdrawal
- The SST is essential in assessing the HPA axis before long-term withdrawal of steroids to avoid adrenal insufficiency 2, 3.
- A study found that immediate and prolonged suppression of the HPA axis is a common finding in patients undergoing systemic steroid treatment, and the low-dose ACTH test can reliably assess this suppression 5.
- The SST can help identify patients who are at risk of adrenal insufficiency after steroid withdrawal, allowing for appropriate management and monitoring 2, 3.
Potential Risks and Considerations
- A personal report described an apparent steroid withdrawal reaction following a short synacthen test, highlighting the potential risks of steroid withdrawal syndrome 6.
- The SST should be performed with caution, and patients should be closely monitored for signs of adrenal insufficiency after steroid withdrawal 2, 3.