Endocrine Abstracts (2015) 38 P316 | DOI: 10.1530/endoabs.38.P316

Does basal post-operative early morning cortisol measurement predict HPA axis integrity as assessed by an insulin tolerance test in patients who have undergone pituitary surgery?

Syed Mustafa Ali Ahmad1, Debbie Papadopoulou1,2, Emma Hatfield1,2, Nigel Mendoza3, Ramesh Nair3, Karim Meeran1,2 & Niamh M Martin1,2


1Section of Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, UK; 2Imperial Centre for Endocrinology, Imperial College Healthcare NHS Trust, London, UK; 3Department of Neurosurgery, Imperial College Healthcare NHS Trust, London, UK.


Background: Correct identification of patients with HPA axis dysfunction following trans-sphenoidal pituitary surgery is important. Our centre measures post-operative day 5 0900 h serum cortisol (24 h after the last dose of glucocorticoid) to identify the need for glucocorticoid replacement. This is given if post-operative day 5 0900 h cortisol concentration is <300 nmol/l, until dynamic pituitary function assessment occurs.

Methods: Data were reviewed for 51 patients undergoing an insulin tolerance test (ITT) ~6 weeks after pituitary surgery (2010–2015) using a new cortisol assay. The peak cortisol concentration during an ITT was compared to post-operative day 5 0900 h serum cortisol.

Results: Of the 27 patients who passed the ITT (peak cortisol >450 nmol/l) 18 had post-operative day 5 0900 h cortisol concentration <300 nmol/l. Of the 24 patients who failed the ITT, seven had post-operative day 5 0900 h cortisol concentrations of >300 nmol/l. The cortisol concentration cut-off point of 300 nmol/l had 70.8% (95% CI: 48.91–87.38%) diagnostic sensitivity and 33.3% (95% CI: 16.52–54.0%) diagnostic specificity. 100% (85.75–100.00%) sensitivity was achieved by increasing the cut-off to 633 nmol/l. Decreasing the cut-off to 101 nmol/l resulted in 100% (87.23–100.00%) specificity. The ROC curve investigating the predictive ability of post-operative day 5 0900 h cortisol had an AUC of 0.60 (95% CI 0.44–0.76).

Conclusions: Following pituitary surgery, post-operative day 5 0900 h cortisol measurement is effective at identifying patients who will subsequently fail an ITT, and hence, require glucocorticoid replacement. However, the current cut-off of 300 nmol/l falsely reassures some patients they do not need glucocorticoid replacement post-operatively.