Endocrine Abstracts

Background: Early morning cortisol levels are commonly used to assess hypothalamo-pituitary-adrenal (HPA) axis function following transsphenoidal pituitary surgery (TSS). Inadequate HPA axis recovery can result in secondary adrenal insufficiency (SAI), a potentially life-threatening complication, requiring glucocorticoid replacement therapy. This need is assessed using early morning postoperative cortisol levels. However, this may be affected by peri-operative dexamethasone administration. Dexamethasone is a long-acting synthetic glucocorticoid that is frequently utilised to decrease post-operative nausea, vomiting and pain. Dexamethasone use will transiently suppress the HPA axis, the extent of which is unknown.

Methods: This is a retrospective cohort study of 71 consecutive patients who underwent TSS at Charing Cross Hospital between 2019 and 2023. The postoperative cortisol level and respective glucocorticoid replacement status of patients who were administered dexamethasone were compared to those who were not. The ability of Day 5, Day 2/3 and Day 4-7 cortisol readings to predict SAI were compared using Receiver Operating Characteristics curves. Samples were analysed using Abbott immunoassays. Dexamethasone was administered to 34 of these patients while the remaining 37 were Late Breaking dexamethasone.

Results: Dexamethasone on induction of general anaesthesia showed no significant impact on Day 5 cortisol levels or the need for replacement glucocorticoid therapy. Day 5 (AUC=0.9645 95% CI 0.9027-1) and Day 4-7 (AUC=0.8679 95% CI 0.7614-0.9743) cortisol provided better predictive value for SAI compared to Day 2/3 samples (AUC=0.8095 95% CI 0.5864-1).

Conclusion: Day 5 cortisol levels have the highest predictive value for SAI and are not significantly affected by the use of dexamethasone on induction.