Endocrine Abstracts

Background: Cushing’s disease (CD) is rare, and standard treatment is trans-sphenoidal surgery (TSS). We previously reported a remission rate of 56% in patients undergoing TSS for CD from a microadenoma/normal pituitary on MR in our unit. Early post-operative hypocortisolaemia performs well at predicting durable remission early on. Post-operative day 1 cortisol of <55 nmol/l has a 100% sensitivity and <138 nmol/l 95% sensitivity at predicting remission. Since October 2021 all patients with CD are operated on by a single neurosurgeon in our unit and we have adopted early post-operative cortisol assessment.

Aims: We retrospectively reviewed the performance characteristics of early post-operative serum cortisol assessment in all patients undergoing TSS for Cushing’s disease at our centre since October 2021.

Methods: Patients do not receive perioperative steroid cover during TSS for microadenoma or normal pituitary MRI and a 0600 h serum cortisol is checked on day 1 post-surgery before starting steroid replacement therapy. Subsequent hormonal assessment (short synacthen testing – SST) occurs 8–10 weeks post-operatively after steroid weaning and if euadrenalism is proven then dynamic testing for steroid excess is undertaken (dexamethasone suppression testing & 24-hour urinary free cortisol estimation).

Results: Nine patients with pituitary microadenoma and 2 patients with normal pituitary MRI underwent pituitary surgery for CD. F:M is 4:1. Day 1 post-operative serum cortisol level, measured in 10 patients, was <50 nmol/l, 50–150 nmol/l and >151 nmol/l for 6, 2 and 2 patients respectively. 10/11 (90%) patients remain in remission post-surgery. Eight patients failed their post-operative SST. Two out of three patients with normal SST post-operatively had normal steroid dynamics as assessed by dexamethasone suppression testing and 24-hour urinary free cortisol estimation. The one patient with ongoing CD did not have day 1 post-operative serum cortisol measurement.

Conclusions: Remission rate in Cushing’s disease in patients with microadenoma or normal pituitary on MRI has improved to 90% in our unit. In our cohort day 1 post-operative serum cortisol level of >150 nmol/l did not predict persistent Cushing’s disease as we observed late remission post TSS in 20% of our cohort.