Variation in response to dexamethasone of a patient with Cushing's syndrome.

A patient with Cushing's syndrome due to a nonresectable chromophobe adenoma underwent external irradiation of the hypothalamic-pituitary area. The signs of Cushing's syndrome ameliorated subsequently but recurred eventually, necessitating bilateral adrenalectomy 30 months after initial presentation. Response to dexamethasone suppression testing on four occasions varied greatly. These results may reflect alterations in sensitivity of the tumour or the hypothalamic-pituitary axis to feedback inhibition by glucocorticoids.