Endocrine Abstracts

Background: Tertiary adrenal insufficiency (TAI) is a complication of long-term exogenous steroid use which results in suppression of the hypothalamic-pituitary-adrenal (HPA) axis. The short synacthen test (SST) is used to assess HPA axis function and recovery during glucocorticoid weaning. This study examined the effect of steroid preparation, dosage and therapy duration on HPA axis suppression.

Method: A retrospective analysis of 950 SSTs performed between 2016 and 2021. Of these 950, 772 (81%) were first SSTs and 178 (19%) were repeat SSTs. Patients under investigation for TAI were identified (n= 512) and included in the analysis, those with suspected primary or secondary adrenal insufficiency were excluded. Data collected included patient demographics, details of steroid use and where available 9am cortisol, baseline ACTH and SST results.

Results: Of the 512 patients 35% failed the SST (peak cortisol <420 nmol/l, ROCHE GEN 2). 33% of those receiving oral steroids had evidence of TAI, compared to 22% and 6% of those receiving inhaled or topical monotherapy, respectively. Most at risk of HPA axis suppression were patients taking combination therapy of oral with either inhaled or topical steroids, with evidence of TAI in 44% and 41% respectively. No patients receiving both topical and inhaled steroids had evidence of TAI. Prednisolone equivalent dose did not differ significantly between those who passed or failed their SST (mean 5.39mg vs 6.01mg, P=.54). Total steroid duration was not a predictor of HPA axis recovery [recovery 63.7 months vs non recovery 70.5 months, P=.64]. 178 repeat SSTs were conducted in 125 patients who failed initial SST. The mean number of repeat SSTs in this cohort was 1.5 (SD 1.1, range 1-8). Overall, 34% of patients undergoing repeat SST demonstrated recovery of the HPA axis with a mean time to recovery of 13.2 months (SD 9.8, range 2.5-49).

Conclusion: Those most at risk of HPA axis suppression are groups on combination therapy of oral with either inhaled or topical preparations, this is of particular relevance to patients with conditions such as asthma or eczema where severe disease can often necessitate dual therapy. 67% of patients on oral steroids had no evidence of TAI. Mean prednisolone equivalent dose or steroid duration did not predict HPA axis recovery. 34% patients undergoing repeat SST testing demonstrated recovery of the HPA axis, indicating that with careful medication adjustment many patients can reverse a suppressed HPA axis.