Post-surgical hypocortisolism after removal of an adrenal incidentaloma : is it predictable by an accurate endocrinological work-up before surgery?

Objective: Few data are available regarding the need of steroid substitutive therapy after unilateral adrenalectomy for adrenal incidentaloma (AI). It is unknown whether, before surgery, the hypothalamic–pituitary–adrenal (HPA) axis secretion parameters can predict post-surgical hypocortisolism. Aim: This study aimed to evaluate whether, in AI patients undergoing unilateral adrenalectomy, post-surgical hypocortisolism could be predicted by the parameters of HPA axis function. Design: Prospective, multicenter. Methods: A total of 60 patients underwent surgical removal of AI (surgical indication: 29 subclinical hypercortisolism (SH); 31 AI dimension). Before surgery, SH was diagnosed in patients presenting at least three criteria out of urinary free cortisol (UFC) levels>60 µg/24 h, cortisol after 1-mg dexamethasone suppression test (1 mg-DST)>3.0 µg/dl, ACTH levels<10 pg/ml, midnight serum cortisol (MSC)>5.4 µg/dl. Two months after surgery, HPA axis function was assessed by low dose ACTH stimulation test or insulin tolerance test when needed: 39 patients were affected (Group B) and 21 were not affected (Group A) with hypocortisolism. The accuracy in predicting hypocortisolism of pre-surgical HPA axis parameters or their combinations was evaluated. Results: The presence of >2 alterations among 1 mg-DST>5.0 µg/dl, ACTH<10 pg/ml, elevated UFC and MSC has the highest odds ratio (OR) for predicting post-surgical hypocortisolism (OR 10.45, 95% confidence interval, CI 2.54–42.95, P=0.001). Post-surgical hypocortisolism was predicted with 100% probability by elevated UFC plus MSC levels, but not ruled out even in the presence of the normality of all HPA axis parameters. Conclusion: Post-surgical hypocortisolism cannot be pre-surgically ruled out. A steroid substitutive therapy is indicated after unilateral adrenalectomy for SH or size of the adenoma.