Adrenocorticotropic hormone-independent bilateral adrenocortical macronodular hyperplasia as a distinct subtype of Cushing's syndrome. Enzyme histochemical and ultrastructural study of four cases with a review of the literature

Cushing's syndrome with cortisol hypersecretion from one of bilateral adrenocortical adenomas: report of a case

We report herein the case of a 40-year-old man with Cushing's syndrome, diagnosed by clinical manifestations and endocrinological studies, who was found to have bilateral adrenocortical adenomas, one of which hypersecreted cortisol. The Cushing's syndrome was therefore attributed to primary adrenocortical disease, and the right adrenal tumor was resected and histologically diagnosed as a so-called black adenoma. After resection of the right tumor, the left adrenal tumor showed no signs of cortisol hypersecretion for the 23 months of follow-up until the patient died of peritonitis subsequent to the rupture of a duodenal ulcer. The left adrenal tumor was examined at autopsy and found to be a cortical adenoma. These data imply that the adrenal adenomas developed primarily from the adrenal gland itself, and that one of the tumors was well differentiated and secreted excess hormones, while the other remained in cell proliferation without hypersecretion.

Gastric inhibitory polypeptide-dependent cortisol hypersecretion--a new cause of Cushing's syndrome

BACKGROUND

Corticotropin-independent nodular adrenal hyperplasia is a rare cause of Cushing's syndrome, and the factors responsible for the adrenal hyperplasia are not known.

METHODS

We studied a 48-year-old woman with Cushing's syndrome, nodular adrenal hyperplasia, and undetectable plasma corticotropin concentrations in whom food stimulated cortisol secretion.

RESULTS

Cortisol secretion had an inverse diurnal rhythm in this patient, with low-to-normal fasting plasma cortisol concentrations and elevated postprandial cortisol concentrations that could not be suppressed with dexamethasone. The cortisol concentrations increased in response to oral glucose (4-fold increase) and a lipid-rich meal (4.8-fold increase) or a protein-rich meal (2.6-fold increase), but not intravenous glucose. The infusion of somatostatin blunted the plasma cortisol response to oral glucose. Intravenous infusion of gastric inhibitory polypeptide (GIP) for one hour increased the plasma cortisol concentration in the patient but not in four normal subjects. Fasting plasma GIP concentrations in the patient were similar to those in the normal subjects; feeding the patient test meals induced increases in plasma GIP concentrations that paralleled those in plasma cortisol concentrations. Cell suspensions of adrenal tissue from the patient produced more cortisol when stimulated by GIP than when stimulated by corticotropin. In contrast, adrenal cells from normal adults and fetuses or patients with cortisol-producting or aldosterone-producing adenomas responded to corticotropin but not to GIP.

CONCLUSIONS

Nodular adrenal hyperplasia and Cushing's syndrome may be food-dependent as a result of abnormal responsiveness of adrenal cells to physiologic secretion of GIP. "Illicit" (ectopic) expression of GIP receptors on adrenal cells presumably underlies this disorder.