54-Year-Old Woman With an Incidentally Discovered Adrenal Mass and Abnormal Dexamethasone Suppression Test: Role of Adrenalectomy

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Mild autonomous cortisol secretion (MACS) is defined as an abnormal cortisol concentration following dexamethasone suppression test (post-DST cortisol >1.8 mcg/dL) and is detected in up to 50% of patients with adrenal cortical adenomas. Patients with MACS present with a higher prevalence of cardiovascular risk factors and events, osteopenia and osteoporosis, and increased risk of fractures. Adrenalectomy leads to improvement of comorbidities in 20%–70% of patients; however, estimating the degree of improvement prior to adrenalectomy is challenging.

Case Report

The patient was a 54-year-old woman who presented for evaluation of continuous weight gain of 50 pounds over 5–7 years. In addition, she had prediabetes (glycosylated hemoglobin = 6%, not on medications) and hypertension treated with metoprolol tartrate 25 mg twice a day and nifedipine 30 mg daily. Two years prior, she was diagnosed with osteoporosis. Several months prior, she was incidentally discovered with a 2.2-cm left adrenal mass initially visualized on chest computed tomography (CT) and further better characterized on abdominal CT ( Fig. 5.1 ). Physical exam was positive for body mass index of 39.8 kg/m ² and blood pressure of 138/86 mmHg, but no features of Cushing syndrome.

INVESTIGATIONS

On unenhanced CT of adrenal glands, the left adrenal mass was lipid rich (6 Hounsfield units [HU]), measuring 2.2 cm in the largest diameter (see Fig. 5.1 ). The right adrenal gland appeared normal. The baseline laboratory test results are shown in Table 5.1 . The serum corticotropin (ACTH) and dehydroepiandrosterone-sulfate (DHEA-S) concentrations were low, and cortisol did not suppress normally with an overnight 1-mg dexamethasone suppression test (DST) (see Table 5.1 ). MACS was diagnosed.

TABLE 5.1

Laboratory Tests

Biochemical Test	Result	Reference Range
1-mg overnight DST, mcg/dL	2.3	<1.8
ACTH, pg/mL	<5	7.2–63
DHEA-S, mcg/dL	26	15–200
Aldosterone, ng/dL	8	<21
Plasma renin activity, ng/mL per hour	4.1	2.9–10.8
Urine metanephrines, mcg/24 h	236	<400
Urine normetanephrine, mcg/24 h	712	<900
Urine free cortisol, mcg/24 h	7.5	3.5–45