Cortisol Testing to Diagnose Adrenal Insufficiency Following Adrenalectomy for Mild Autonomous Cortisol Secretion

Context Patients with mild autonomous cortisol secretion (MACS) can develop adrenal insufficiency after unilateral adrenalectomy. Objective To determine prevalence, duration, and predictors of adrenal insufficiency, and compare postoperative basal cortisol and cosyntropin stimulation test (CST). Design and participants. In this multicenter retrospective study of patients with MACS, adrenal insufficiency was diagnosed when postoperative basal cortisol was <10 µg/dL and/or CST<18 µg/dL. The results were concordant when both tests met cut-offs. Biochemical (BSS) and clinical (CSS) severity scores were calculated. Results Among 281 patients with MACS (80% women), postoperative adrenal insufficiency was diagnosed in 153 (54.5%) patients. Adrenal insufficiency inversely correlated with age (odds ratio [OR] 0.67 per 10 years, 95% CI 0.53–0.84). Low basal cortisol and CST were associated with younger age (OR 0.64 per 10 years for both) and higher BSS (OR 1.17 and 1.22, respectively). Basal cortisol and CST were discordant in 22% of patients, and the discordance rate was more common in patients with bilateral nodules (32% vs 19%, P<.001). The median time to adrenal insufficiency recovery was 3.9 months (IQR, 3–5.9), with longer duration associated with higher BSS and CSS: 3 months for mild, 4-5 months for moderate, and 12-14 months for severe BSS and CSS. Conclusions Approximately half of patients with MACS developed postoperative adrenal insufficiency, with 50% recovering by 3.9 months after surgery. BSS correlated with basal cortisol, CST, and duration of adrenal insufficiency. As discordant results were noted in 22%, performing both basal cortisol and CST postoperatively should be considered.