Endocrine Abstracts

Background: After pituitary surgery patients require HPA axis assessment, that is achieved with postoperative cortisol measurements and, in selected patients whose post-operative cortisol measurements are inconclusive, with the insulin tolerance test (ITT) and the glucagon stimulation test (GST).

Aim: We aimed to assess the performance of the day 2/3 post-operative cortisol in predicting the HPA axis sufficiency as assessed by the ITT and the GST.

Methods: Retrospective review of all pituitary surgical records done in 2004–2014 in a tertiary centre.

Results: 71 patients met the inclusion criteria, out of which 41 (57.7%) had an ITT and 30 (42.3%) a GST. 0900 h cortisol measurements on day 2/3 postoperatively did not differ between the patients having an ITT or a GST (353±188 vs 348±194, P 0.85). Peak cortisol measurements post dynamic testing were 549±218 for ITT and 458±241 for GST. ROC curve analysis showed that day 2/3 postoperative cortisol of ≤142 nmol/l was 100% (84–100%) sensitive in detecting patients that would fail the ITT, with 31% (14–56%) specificity, and a cut-off of ≥470 nmol/l was 94% (69–100%) specific in identifying patients with ACTH sufficiency with 32% (17–52%) sensitivity. When applying the same cut-offs in GST, a day 2/3 cortisol of ≤142 nmol/l was 93% (62–100%) sensitive in detecting patients that would fail the GST, with 28% (12–51%) specificity, and a cut-off of ≥470 nmol/l was only 78% (54–91%) specific in identifying patients with ACTH sufficiency with 50% (26–75%) sensitivity.

Conclusion: After pituitary surgery a day 2/3 postoperative cortisol of ≤142 nmol/l detects all patients with ACTH insufficiency, and a cortisol of 470 nmol/l excludes ACTH insufficiency.