Nonfunctional adrenal adenomas and impaired glucose metabolism: a systematic review and meta-analysis

Purpose Evidence on nonfunctioning adrenal incidentaloma's (NFAI) associated comorbidities and in particular, glucose disorders, is unclear in contrast to adrenal tumors with mild autonomous cortisol secretion. The current systematic review and meta-analysis aimed to assess the burden of impaired glucose metabolism including diabetes mellitus type 2 (T2DM), fasting blood glucose (FBG), and fasting blood insulin (FBI) levels in patients with NFAI and 1-mg overnight dexamethasone suppression test (ODST) <= 1.8 mu g/dl across published studies. Methods We searched PubMed, Cochrane, and Scopus databases for identifying studies published between 1956 and March 2021. Twenty-five studies met the selection criteria including prospective, retrospective, and case-control studies. Two reviewers independently extracted studies, participants' characteristics and outcome data in a total pooled sample of 1548 patients. Results Patients with NFAI had twofold [(odds ratio (OR) (95% confidence interval (CI)): 2.03 (1.39-2.98)] increased odds to present T2DM as well as higher FBG [weighted mean difference (WMD) (95% CI): 3.85 (1.96-5.74)] and homeostasis model assessment (HOMA) [WMD (95% CI): 0.68 (0.23-1.12)] with respect to controls. On the contrary, the WMD of FBI levels did not differ between the two groups. The incidence of T2DM in a subgroup analysis of patients with NFAI without glucose disorders at baseline was 6% [pooled incidence (95% CI): 0.06 (0.04-0.09)]. Conclusions Patients with NFAI and 1-mg ODST <= 1.8 mu g/dl presented higher odds of T2DM and higher levels of FBG and HOMA index than healthy controls.