Transsphenoidal surgery for Cushing's disease: the role of early post-operative serum cortisol measurements as a predictor of success--a prospective study.

INTRODUCTION Transsphenoidal surgery (TSS) is the treatment of choice for Cushing`s disease (CD). A proper assessment of the efficacy of surgical treatment is crucial in terms of patient prognosis. The aim of this study was to evaluate the usefulness of serum cortisol measurements performed on the first post-operative day as a predictor of TSS outcome. MATERIAL AND METHODS This prospective study involved 36 patients with CD who were operated on using the same surgical protocol and followed up for at least 18 months (median: 30 months). We investigated the relationship between serum cortisol measurements performed on the first post-operative day and the hormonal assessment of the pituitary-adrenal axis performed after 18 months of follow-up. The adopted criteria for remission were: serum cortisol within the referral range, normal circadian rhythm, and the ability of serum cortisol to suppress to values ≤ 1.8 μg/dL after 1 mg of dexamethasone. RESULTS The median serum cortisol on the first post-operative day was 1.98 μg/dL. 23 patients (63.9%) were regarded as cured. In all these cured cases, the post-op cortisol was ≤ 2.5. On the other hand, in the cases of the 13 patients (36.1%) for whom the remission of CD was not confirmed, the post-op cortisol was ≥ 2.5. CONCLUSION Our prospective study demonstrated that early post-operative serum cortisol measurements can serve as a simple and useful test that predicts the remission of CD. Furthermore, a post-operative cortisol ≤ 2.5 can be considered as a forecast of CD remission.