Aberrant hormone receptors have been demonstrated in macronodular adrenal hyperplasia or, rarely, unilateral adenomas causing Cushings syndrome but their prevalence in adrenal incidentalomas (AI) remains uncertain. Therefore we evaluated patients with bilateral AI for evidence of abnormal response to physiological stimuli. We also compared their biochemical characteristics with those of patients with unilateral AI.
Assessment of adrenal function was performed in 93 patients (27 men, 66 women, mean age 59.2+/−12 years) with AI; 27 patients (29%) with bilateral (Group A) and 66 patients with unilateral adenomas (Group B). Non-diabetic patients (n=68) underwent a 75g-OGTT. Eighteen patients of Group A were submitted to a meal test and 15 to a posture test. The posture test was positive in 3/15 (20%) patients and the meal test in 1/18 (5.5%). The size of the largest adenoma in Group A was significantly greater compared to Group B (3.1+/−1.1 vs. 2.3+/−1.1, P=0.01). No significant difference regarding the mean levels of UFC, ACTH, DHEAS and midnight cortisol existed between the groups. A significantly greater proportion of Group B patients had fully suppressed cortisol levels (<1μg/dl) post-LDDST (37.9% vs. 14.8% for Group A, P=0.023). The prevalence of diabetes and hypertension and mean glucose levels during OGTT were similar among groups, but in Group B the HOMA-R was significantly higher (2.74+/−1.3 vs. 1.89+/−0.78 P=0.037) and the QUICKI and ISI-composite indices significantly lower (0.33+/−0.03 vs. 0.35+/−0.03, P=0.046 and 3.3+/−1.5 vs. 4.7+/−2, P=0.016).
In conclusion, evidence for aberrant responses to physiological stimuli, particularly to upright posture, is occasionally found in patients with bilateral AI. Although there are no major biochemical differences between subjects presenting with bilateral or unilateral lesions, bilateral lesions tend to be larger and are more often associated with lack of dexamenthasone suppression whereas unilateral adenomas are more related to increased insulin resistance.