A case of autonomous cortisol secretion in a patient with subclinical Cushing's syndrome, GNAS mutation, and paradoxical cortisol response to dexamethasone

Background Increased urinary free cortisol in response to the oral administration of dexamethasone is a paradoxical reaction mainly reported in patients with primary pigmented nodular adrenocortical disease. Here, we describe the first case of subclinical Cushing’s syndrome represented by autonomous cortisol secretion and paradoxical response to oral dexamethasone administration, harboring an activating mutation in the α subunit of the stimulatory G protein (GNAS).