Adrenal Incidentalomas are Tied to Increased Risk of Diabetes: Findings from a Prospective Study

Context: The frequency of adrenal incidentalomas and their association with comorbid conditions have been assessed mostly in retrospective studies that may be prone to ascertainment bias.

Objective: The objective of this work is to evaluate the frequency of adrenal incidentalomas and their associated comorbid conditions.

Design: A prospective cohort study was conducted.

Setting: This study took place at a radiology department at a public hospital.

Participants: Unselected outpatients who underwent an abdominal computed tomography (CT) from January 2017 to June 2018. Patients with known or suspected adrenal disease or malignancy were excluded.

Exposure: All abdominal CT scans were evaluated by an experienced radiologist. Hormonal workup including a 1-mg dexamethasone suppression test was performed in patients bearing adrenal incidentalomas.

Main outcome and measure: Frequency of adrenal incidentalomas in abdominal CT of unselected patients; frequency of comorbid conditions, and hormonal workup in patients bearing adrenal incidentalomas.

Results: We recruited 601 patients, and in 7.3% of them an adrenal tumor was found serendipitously. The patients bearing an adrenal incidentaloma had higher body mass index (P = .009) and waist circumference (P = .004) and were more frequently diabetic (P = .0038). At multivariable regression analysis, diabetes was significantly associated with the presence of adrenal incidentalomas (P = .003). Autonomous cortisol secretion was observed in 50% of patients who did not suppress cortisol less than 50 nmol/L after 1 mg dexamethasone.

Conclusions: The frequency of adrenal incidentalomas is higher than previously reported. Moreover, adrenal incidentalomas are tied to increased risk of type 2 diabetes. This finding is free from ascertainment bias because patients with adrenal incidentalomas were drawn from a prospective cohort with the same risk of diabetes as the background population.