Maximum adenoma diameter, regardless of uni- or bilaterality, is a risk factor for autonomous cortisol secretion in adrenal incidentalomas

Purpose: To evaluate differences between patients with unilateral and bilateral adrenal incidentalomas (AIs) in the prevalence of autonomous cortisol secretion (ACS) and related comorbidities. Methods: In this multicentre retrospective study, AIs ≥ 1 cm without overt hormonal excess were included in the study. ACS was defined by a post-dexamethasone suppression test (DST) serum cortisol ≥ 5.0 µg/dl, in the absence of signs of hypercortisolism. For the association of ACS with the prevalence of comorbidities, post-DST serum cortisol was also analysed as a continuous variable. Results: Inclusion criteria were met by 823 patients, 66.3% had unilateral and 33.7% bilateral AIs. ACS was demonstrated in 5.7% of patients. No differences in the prevalence of ACS and related comorbidities were found between bilateral and unilateral AIs (P> 0.05). However, we found that tumour size was a good predictor of ACS (OR = 1.1 for each mm, P< 0.001), and the cut-off of 25 mm presented a good diagnostic accuracy to predict ACS (sensitivity of 69.4%, specificity of 74.1%). Conclusions: Tumour size, not bilaterality, is associated with a higher prevalence of ACS. During follow-up, neither tumour size nor bilaterality were associated with the development of new comorbidities, yet a larger tumour size after follow-up explained the association of bilateral AIs with the risk of dyslipidaemia.