Endocrine Abstracts

Introduction: The majority of adrenocortical incidentalomas (AIs) are nonfunctional adenomas. Some of them demonstrate an autonomous cortisol secretion (ACS), a pathologic condition defined as biochemical evidence of hypercortisolism without typical signs or symptoms of Cushing’s syndrome.

Subjects and methods: In this cross-sectional study, we evaluated 152 consecutive patients, aged 58.3 years (range, 25-84 years) of whom 105 (69.1%) with unilateral adrenal incidentalomas (UAIs) and 47 (30.9%) with bilateral adrenal incidentalomas (BAIs). The hypothalamic-pituitary-adrenal (HPA) axis activity was evaluated using basal cortisol and ACTH levels, midnight cortisol level, 24-h urinary free cortisol (UFC), and post 1 mg overnight dexamethasone suppression test (1 mg-DST) cortisol level. We measured the maximum adrenal nodule diameter on CT and MRI.

Results: There was no significant difference between the longest diameter of the largest adrenal nodule between BAI and UAI patients (3.2 ± 1.0 vs 3.0 ± 1.2mm P=0.254). We found that the maximum adrenal nodule diameter negatively correlated with the ACTH level (r=-0.213; P=0.009), and positively correlated with midnight serum cortisol level (r=0.274; P=0.001), UFC (r=0.264; P=0.044), post DST-1 mg cortisol level (r=0.206; P=0.011), and probability for ACS (r=0.276; P=0.001). Multivariate Logistic Regression for ACS showed, after controlling for age, waist circumference, Body Mass Index, UAI vs BAI, that adrenal adenoma size was an independent predictor of occurrence of ACS (OR=1.055, 95% CI 1.017-1.094, P=0.004).

Conclusion: These results suggest that critical adrenal tumor mass is required to increase the capacity of steroidogenesis and to result in mild cortisol excess, but probably different pathogeneses are also involved.