Coexistence of Cushing Disease With a Solitary Adrenocorticotrophic Hormone-Dependent Adrenal Adenoma

OBJECTIVE: We report a 49-year-old woman who had minimal features of Cushing syndrome and an incidentally discovered adrenal adenoma. She was subsequently diagnosed with pituitary-dependent Cushing syndrome. METHODS: Laboratory and imaging studies including serum cortisol, plasma adrenocorticotrophic hormone (ACTH), high dose dexamethasone test, corticotropin-releasing hormone test, computed tomography (CT) scan, and magnetic resonance imaging were performed. RESULTS: A 49-year-old woman was admitted for urosepsis. An abdominal CT scan performed during the urosepsis workup showed a 2.7-cm right adrenal adenoma. She denied any abdominal striae or other symptoms. Physical examination showed normal vital signs, minimal facial fullness without central obesity, and striae. Laboratory results were as follows: 24-hour-urine cortisol 294 μg (reference 4.0-50.0), midnight serum cortisol 23.0 μg/dL (reference < 7.5), and plasma ACTH level 39 pg/mL (reference 5-27). A corticotropin-releasing hormone stimulation test showed >20% rise in serum cortisol and >35% rise in ACTH levels. A pituitary magnetic resonance image showed a 5 mm pituitary lesion. The patient underwent transsphenoidal pituitary surgery, which confirmed an ACTH-secreting lesion. Postoperatively, she required hydrocortisone replacement for the next 10 months. A follow-up adrenal CT performed 6 months later showed a decrease in the size of the adrenal adenoma (1.8 cm). CONCLUSION: This case highlights the importance of recognizing the coexistence of ACTH-dependent Cushing disease with an adrenal adenoma and partial ACTH dependency of the adrenal adenoma.