Purpose: The postoperative course of renal function remains unclear in Cushing syndrome. We examined changes in renal function after adrenalectomy in patients with Cushing syndrome and attempted to identify predictors of renal impairment. Methods: The study population comprised 76 patients who underwent adrenalectomy for Cushing and subclinical Cushing syndrome between 2001 and 2018. Renal function and other factors were evaluated pre-operation, at 1 postoperative month, and 1 postoperative year. We defined a ≥10% decrease in the estimated glomerular filtration rate at 1 postoperative year as renal impairment, and predictors associated with this reduction were investigated. The relationship between renal function and steroid replacement after surgery was also examined. Results: Mean pre-operative estimated glomerular filtration rate was 82.2 ml/min/1.73 m2. While mean estimated glomerular filtration rate was significantly lower at 1 postoperative month than the pre-operative value (71.7 ml/min/1.73 m2 [89.1%], p < 0.001), no significant differences were observed between 1 postoperative year and pre-operation (79.5 ml/min/1.73 m2 [97.6%], p = 0.108). Twenty-six patients (34.2%) developed renal impairment. A multivariate analysis identified a low pre-operative adrenocorticotropic hormone level as an independent predictor of renal impairment (odds ratio 6.30, p = 0.031). Among 43 patients with available records of steroid replacement history, 18 (41.9%) developed renal impairment. The ratio of patients with a reduced steroid replacement dose at 1 postoperative month was significantly lower among patients with renal impairment than those without (22.2% vs. 56.0%, p = 0.027). Conclusions: The pre-operative adrenocorticotropic hormone level was a predictor of renal function after adrenalectomy in patients with Cushing or subclinical Cushing syndrome.
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