Table 2.

Diagnose of Adrenal Incidentalomas with Endocrinological Investigation.

	Number (%)
Pheochromocytoma	8 (13.1%)
Primary aldosteronism	15 (24.6%)
Prevalence with our criteria of sub-clinical Cushing’s syndrome.
Cortisol secreting adenoma	13 (21.3%)
Cushing’s syndrome	3 (4.9%)
Sub-clinical Cushing’s syndrome	10 (16.4%)
Non-functioning tumor	25 (41.0%)
Prevalence with the criteria of sub-clinical Cushing’s syndrome widely used in Japan.
Cortisol secreting adenoma	8 (13.1%)
Cushing’s syndrome	3 (4.9%)
Sub-clinical Cushing’s syndrome	5 (8.2%)
Non-functioning tumor	30 (49.2%)

The dissimilarity between our criteria of sub-clinical Cushing’s syndrome and the criteria widely used in Japan was the positive value of patients’ serum cortisol levels after 1 mg dexamethasone suppression test (DST). In our criteria, patients’ serum cortisol levels ≥ 1.8 μg/dL after 1 mg DST were positive for diagnosis of sub-clinical Cushing’s syndrome if satisfying both lower morning ACTH level instead of normal or high levels, and loss of diurnal serum cortisol rhythm. In the criteria widely used in Japan, patients’ serum cortisol levels ≥3.0 μg/dL after 1 mg DST were positive for diagnosis of sub-clinical Cushing’s syndrome.