Corticotropin-independent macronodular adrenal hyperplasia associated with insulinoma

To report a case of corticotropin-independent macronodular adrenal hyperplasia (AIMAH) associated with an insulinoma.

We describe the clinical, radiographic, laboratory, and histopathologic findings of the study patient; review the current protocols for management of AIMAH; and discuss the disease etiology.

A 64-year-old woman with multiple intradermal facial nevi experienced intermittent light-headedness, tremor, and confusion and was found to have a venous plasma glucose concentration of 52 mg/dL. Hypoglycemia and hyperinsulinemia after 18 hours of fasting suggested the presence of an insulinoma. Hepatic venous sampling for insulin after selective arterial calcium injection localized the insulinoma to the pancreatic head. The insulinoma was excised, and there was no recurrence over the 5 years the patient was in our care. During the workup for insulinoma, bilateral adrenal masses were incidentally discovered on computed tomography. Twenty-hour urinary free cortisol excretion was elevated and serum corticotropin was suppressed. Overt signs of Cushing syndrome were not present, and subsequent urinary cortisol measurements were within the reference range for several years. After 4 years, Cushing syndrome developed and bilateral adrenalectomy was performed. AIMAH was diagnosed on the basis of histopathologic findings.

This appears to be the first reported case of AIMAH associated with an insulinoma. In the absence of other stigmata of multiple endocrine neoplasm type 1 and in the presence of multiple nevi, it may represent a novel endocrine syndrome.