A case of Cushing's disease associated with a non-functioning adrenal tumor

A 52-year-old woman was admitted to our hospital for further examination of central obesity, hypertension and hirsutism suggesting Cushing's syndrome. Hirsutism had been remarkable for two years, and muscle weakness of the lower extremities gradually developed during the past year. CT scan revealed a tumor in the left adrenal gland which was 1 cm in diameter, round, well-circumscribed, homogeneous and not enhanced. Endocrine data disclosed increased urinary 17-OHCS (11.5-16.4 mg/day) and elevated plasma ACTH (125 pg/ml) and cortisol (19 micrograms/dl) with a lack of diurnal rhythm. Administration of the single-dose dexamethasone (1mg) did not suppress plasma cortisol. However, consecutive administration of either 2mg or 8mg of dexamethasone for 2 days suppressed both plasma cortisol and urinary 17-OHCS. Administration of metyrapone raised both urinary 17-OHCS and plasma ACTH levels. Rapid ACTH test resulted in a hyperresponse of plasma cortisol. CRF injection raised plasma ACTH and cortisol. Bilateral adrenal glands were well demonstrated by 19-iodocholesterol (I-131) scintigraphy during the administration of dexamethasone. MRI with Gd-contrast revealed a microadenoma in the sella turcica. With the diagnosis of Cushing's disease, the microadenoma was removed by the transsphenoidal approach and adrenal function was normalized. However, the left adrenal tumor remained on CT scan but was not demonstrated by scintigraphy. These findings indicate that this is a very rare case of Cushing's disease which was associated with an unilateral non-functioning adrenal tumor.