Analysis of clinical and pathological features of primary bilateral macronodular adrenocortical hyperplasia and unilateral adrenal adenoma

Background Primary bilateral macronodular adrenocortical hyperplasia (PBMAH) is a rare condition with untypical subclinical symptoms of Cushing's syndrome (CS). This study aimed to compare the clinical and pathological features of PBMAH with unilateral cortisol-secreting adrenal adenoma (UAA). Methods We prospectively included 46 PBMAH patients and 205 UAA patients from January 2000 to February 2014. Cortisol levels and 24 hours urine free cortisol (UFC) were determined at baseline and during dexamethasone suppression test (DST) using the chemiluminescence method. Computed tomography (CT) examination of the adrenal glands was performed in all patients. For patients treated with adrenalectomy, hematoxylin, and eosin, staining was performed for pathological examination. Results The proportion of patients with autonomous cortisol secretion was significantly higher in PBMAH patients (39.1%) than UAA patients (6.8%). The PBMAH patients showed significantly lower levels of basal cortisol, low dose dexamethasone suppressed cortisol, and high dose dexamethasone suppressed cortisol than the UAA patients (452.6±183.3 vs. 578.7±166.4 nmol/L, P=0.003; 394.5±298.9 vs. 549.2±217.7 nmol/L, P=0.002; 397.3±282.3 vs. 544.3±187.6 nmol/L, P=0.003). Similarly, the PBMAH patients had significantly lower levels of basal 24 hours UFC, low dose dexamethasone suppressed 24 hours UFC, and high dose dexamethasone suppressed 24 hours UFC than the UAA patients (1,144.4±1,048.1 vs. 1,674.9±1,520.4 nmol/24 h, P=0.032; 1,157.3±1,483.5 vs. 1,940.1±1,360.9 nmol/24 h, P=0.003; 1,256.4±1,767.0 vs. 1,969.9±1,361.7 nmol/24 h, P=0.011). Conclusions PBMAH is often associated with atypical CS symptoms. The clinical and imaging features of PBMAH are useful for the differential diagnosis of this disease.