High Cortisol Concentration Without Cushingoid Appearance

A 53-year-old man was referred to us for evaluating left adrenal incidentaloma. His morning plasma adrenocorticotropic hormone (ACTH) and serum cortisol levels were 42.5 pg/mL and 30.2 μg/dL, respectively, indicating ACTH-dependent hypercortisolemia. The patient did not exhibit any Cushingoid features, but had mild gynecomastia (Figure). His serum prolactin (PRL) levels were slightly elevated (19.1 ng/mL), whereas estrogen levels were not (9 pg/mL). His testosterone levels were within the normal range (3.40 ng/mL). The 1-mg overnight dexamethasone suppression test did not suppress serum cortisol levels (6.0 μg/dL), despite reducing ACTH levels (1.9 pg/mL). His late-night plasma ACTH and serum cortisol levels were 5.7 pg/mL and 8.0 µg/dL, respectively, indicating autonomous cortisol secretion. However, urinary free cortisol levels were 45.6 μg/day (reference range: 11.2-80.3), suggesting no cortisol over-secretion. Although the serum cortisol levels were high on multiple occasions, his serum electrolytes and white blood cell fractions were within normal limits. No overt metabolic abnormalities were observed. All other hormone levels were within normal ranges …