Corticotropin-Independent Cushing Syndrome in a Patient With “Normal” Adrenal Imaging

The diagnosis of corticotropin (ACTH)-independent hypercortisolism with adrenal imaging that does not demonstrate unilateral or bilateral nodules should prompt consideration of bilateral micronodular hyperplasia (Table C.2). Primary pigmented nodular adrenocortical disease (PPNAD) may be isolated or part of Carney complex.

Case Report

The patient was a 20-year-old woman who has been referred to endocrinology after developing unexplained avascular necrosis of the hips. On interview, she reported a progressive weight gain of 75 pounds over 18 months; development of striae over her arms, abdomen, back, and hips, development of dorsocervical and supraclavicular pads; rounding and erythema of the face; and intensification of anxiety. In addition, she noticed difficulties keeping up with her training in the nursing school due to progressive fatigue and decrease in concentration. She reported a remote exogenous glucocorticoid use history (two hip injections 3 years prior). Medical history was positive for low bone mass on bone mineral density testing (T scores of −1.3), avascular necrosis of the hips, and anxiety. The family history was negative for adrenal disorders. On physical examination, her body mass index was 32 kg/m ² and blood pressure was 136/87 mmHg. Physical examination demonstrated abdominal fat redistribution with obesity, prominent supraclavicular and dorsocervical pads, facial rounding, and striae. Skin examination revealed several café-au-lait lesions on the neck.

INVESTIGATIONS

Owing to a high clinical suspicion for Cushing syndrome (CS), laboratory workup was initiated, which confirmed glucocorticoid autonomy ( Table 19.1 ). An unenhanced adrenal-dedicated computed tomography (CT) scan was initially interpreted as normal, although on closer examination it showed micronodular thickening of both adrenal glands ( Fig. 19.1 ). PPNAD was suspected, and bilateral adrenalectomy was recommended.

TABLE 19.1

Laboratory Tests

Biochemical Test	Result	Reference Range
1-mg overnight DST, mcg/dL	9	<1.8
8-mg overnight DST, mcg/dL	13	<1
Morning serum cortisol, mcg/dL	8	7–25
ACTH, pg/mL	<5	7.2–63
DHEA-S, mcg/dL	37	44–332
Urine free cortisol, mcg/24 h	22	3.5–45
Midnight salivary cortisol, ng/dL	60	<100