Endocrine Abstracts

Introduction: Assessing cortisol status is a key endocrine investigation, to identify those who need glucocorticoid replacement or emergency sickness cover either due to primary or secondary cortisol deficiency or after long-term/high dose steroid treatment causing Hypothalamic-Pituitary-Adrenal axis (HPAA) suppression. A short synacthen test (SST) measuring cortisol levels after administration of Synthetic ACTH at time zero, 30 and 60 minutes is commonly used. A normal response is assay dependent, for our institution historically > 500 nmols/l; >420 nmols/l from Dec 2015 (Roche Gen II).

Aim: To examine the SST response in patients investigated for primary, secondary/tertiary hypoadrenalism or adrenal suppression secondary to exogenous steroids.

Methods: All SSTs and clinical indication were identified from our departmental database between 1/10/2005 and 1/6/2016.

Results: 512 consecutive SSTs (437 patients, M=183) were identified, undertaken at various times of day. 382 patients had one test, 41 patients two tests, 8 patients three tests and 6 patients four tests. Median(range) age was 11.3(0.01–21.5) years. Indication and results for SST were; suspected HPAA suppression from exogenous steroids (patients n=139, 82/185 tests, 44% abnormal), suspected secondary/tertiary hypoadrenalism (patients n=181, 36/205 tests, 18% abnormal), suspected primary hypoadrenalism (patients n=73, 13/76 tests, 17% abnormal) and other indication (including chronic fatigue, hypoglycaemia) (patients n=44, 4/46 tests 9% abnormal). Overall, in abnormal and normal tests the cortisol peak was at 60 minutes (n=491), 30 minutes (n=19), at time zero (n=2). 377 tests showed a normal cortisol response with cortisol peak at 30 minutes in n=17 but all also had cortisol normal response at 60 minutes. Peak cortisol by clinical indication; suspected HPA axis suppression from exogenous steroids: 30 min n=6, 60 min n=179, suspected secondary or tertiary hypoadrenalism: 30 min n=8, 60 min n=197, suspected primary hypoadrenalism: zero min n=2, 30 min n=4, 60 min n=70, other indication: 30 min n=1, 60 min n=45.

Conclusion: In 96% of SSTs, the diagnostic cortisol peak was at 60 minutes. All of the normal tests with the highest peak at 30 minutes also demonstrated an adequate response by 60 minutes. This study questions the need for a 30 minute cortisol measurement during a SST.