Endocrine Abstracts

JOINT104

Introduction: Glucocorticoids (GC) are widely used in managing chronic inflammatory conditions. Long-term exposure to GC leads to HPA axis suppression. Recovery of HPA axis is highly variable among patients and often Short Synacthen test (SST) is used in standard practice to assess HPA axis and to assist wean off glucocorticoids. This test requires a day care investigation unit and has cost implications. The joint clinical guideline by European Society of Endocrinology and Endocrine Society published in May 2024 addresses the management of this condition. Our aim was to assess the applicability of criteria suggested in the guideline to our patient population, accepting there is variability in cortisol assays.

Method: This is a retrospective study of 48 patients with GC induced adrenal insufficiency who underwent outpatient morning SST (IM tetracosactide 250 μg) at Aintree University Hospital, Liverpool, UK from February 2022 to January 2024. Pass result for SST (HPA axis recovery) was determined as 30-minute cortisol ≥ 450 nmol/l. We use a competitive immunoassay (electrochemiluminescence – Roche Gen 2) for cortisol measurements.

Results: There was a significant and strong positive relationship between morning cortisol and 30-min cortisol on SST (rs[46]=0.82, P-value<0.001). Statistically significant difference (P-value<0.001) was observed in the 0900 h cortisol of those patients who passed SST (median 308 nmol/l) compared to those who failed (median 154 nmol/l). Morning cortisol >300 nmol/l is more likely to predict HPA axis recovery (P-value<0.001, Specificity 96%, PPV 92%). Meanwhile morning cortisol of <150 nmol/l is highly likely to predict adrenal insufficiency (P-value=0.001, Specificity 95%, PPV 93%). Among patients with morning cortisol between 150 and 300 nmol/l, there was no significant difference noted as 59% failed SST and 41% passed the SST.

Conclusion: Our study shows a linear relationship between morning cortisol and 30-minute cortisol on SST and the likelihood of passing the SST. This supports the guideline’s emphasis to interpret 0900 h cortisol as a continuum with higher values are more indicative of HPA axis recovery. Morning median cortisol in our study was significantly different in those who passed SST compared to those who failed. They were very reflective of the cut offs values suggested in the guideline. Morning cortisol threshold >300 nmol/l and <150 nmol/l were statistically significant in our study to predict HPA axis outcome with high specificity and positive predictive values. SST use may therefore be limited for selective patients with borderline cortisol results needing GC withdrawal soon based on their clinical needs.