Screening for HPA Suppression in Chronic Steroid Therapy
Screen for HPA axis suppression only after glucocorticoids have been tapered to physiologic doses (≤5 mg prednisone daily or equivalent), using an early morning serum cortisol measured between 8:00-9:00 AM, at least 24 hours after the last glucocorticoid dose. 1
When NOT to Screen
Do not routinely test for adrenal insufficiency in the following situations:
- Patients still on supraphysiologic doses (>5-6 mg prednisone equivalent daily) 1
- Patients who still require glucocorticoids for their underlying disease 1
- Short-term therapy <3-4 weeks, regardless of dose—glucocorticoids can be stopped without testing 1
The 2024 European Society of Endocrinology/Endocrine Society joint guideline emphasizes that testing while on supraphysiologic doses is not clinically useful, as these patients are expected to have suppressed axes 1.
When to Screen
Initiate screening when:
- Glucocorticoids have been tapered to physiologic replacement doses (prednisone 4-6 mg daily or hydrocortisone 15-25 mg total daily) 1
- The underlying disease is controlled and no longer requires glucocorticoid treatment 1
- Biochemical confirmation of HPA recovery is desired before complete discontinuation 1
The Screening Test
Morning serum cortisol is the recommended first-line test 1:
Test Specifications:
- Draw between 8:00-9:00 AM
- Hold glucocorticoid dose for at least 24 hours before testing (except dexamethasone, which requires longer washout) 1
- Patient must be on physiologic dose equivalent (≤5-6 mg prednisone) 1
Interpretation (as a continuum, not rigid cutoffs):
Cortisol >300 nmol/L (10 μg/dL):
- Indicates HPA axis recovery
- Glucocorticoids can be safely discontinued 1
Cortisol 150-300 nmol/L (5-10 μg/dL):
- Continue physiologic glucocorticoid replacement
- Repeat morning cortisol every few weeks to months 1
- Dynamic testing may be considered but is not routinely recommended 1
Cortisol <150 nmol/L (5 μg/dL):
- Very likely persistent adrenal insufficiency
- Continue physiologic glucocorticoid replacement
- Repeat morning cortisol after a few months (1-6 months depending on prior trajectory) 1
- Dynamic testing unlikely to be useful 1
Important Caveats
The guideline explicitly states that biochemical testing is sensitive but not specific 1. The risk of clinically meaningful adrenal insufficiency and adrenal crisis remains very low even among those with biochemical insufficiency. Testing provides a safeguard but is not a prerequisite for continued tapering 1.
Dynamic testing (ACTH stimulation) is NOT routinely recommended 1. The 2024 guidelines suggest against routine dynamic testing for patients tapering or stopping glucocorticoids.
Special Populations Requiring Heightened Awareness
Consider possible glucocorticoid-induced adrenal insufficiency in patients with: 1
- Non-oral glucocorticoid formulations (inhaled, topical, nasal, intra-articular) presenting with symptoms
- Multiple simultaneous glucocorticoid formulations
- High-dose inhaled or topical glucocorticoids
- Inhaled/topical glucocorticoids for >1 year
- Intra-articular injections within previous 2 months
- Concomitant strong CYP3A4 inhibitors
- Signs/symptoms of exogenous Cushing syndrome (assume adrenal insufficiency) 1
Alternative Approach: Clinical Monitoring
The guidelines offer two acceptable strategies 1:
- Biochemical confirmation: Test with morning cortisol as described above
- Clinical monitoring: Continue gradual taper while monitoring clinically for signs/symptoms of adrenal insufficiency
This reflects the reality that biochemical adrenal insufficiency is common but clinically significant adrenal crisis is rare in this population 1.
Factors That Do NOT Predict HPA Recovery
Research shows no correlation between adrenal function recovery and: 2
- Age
- Sex
- Indication for glucocorticoid therapy
- Duration of corticosteroid therapy
- Cumulative dose
- Daily dose (once at physiologic levels)
However, body mass index showed positive correlation with cortisol response 2, and basal cortisol levels are predictive of HPA axis function 3.
Practical Considerations
Confounding factors affecting cortisol measurement: 1
- Disrupted circadian rhythm (night shift workers, jet lag, severe insomnia) can falsely lower morning cortisol
- Elevated cortisol-binding globulin (pregnancy, oral estrogens) can falsely elevate serum cortisol
- Decreased cortisol-binding globulin can falsely lower serum cortisol
Long-acting glucocorticoids: Switch patients from dexamethasone or betamethasone to shorter-acting agents (hydrocortisone or prednisone) before attempting to assess HPA recovery 1.
The FDA label confirms that recovery time for normal HPA activity is variable depending on dose and duration, and patients remain vulnerable to stress during this period 4.