Endocrine Abstracts

Distinguishing Cushing disease from pseudo-Cushing syndrome still remains a challenge, especially in some specific cases when absorption or compliance of dexamethasone used in diagnostical tests are questionable. Several versions of an intravenous (IV) test have been utilized and serve both in the initial and differential diagnosis of Cushing’s syndrome.

We report a 59-year-old patient with macroadenoma of pituitary gland (revealed accidentally on MRI due to dizziness and headaches) 26×18 mm in size, compressing infundibulum and sella, probably adenoma according to radiological characteristics. Her medical history revealed surgical resection of stomach due to a gastrointestinal stromal tumor (GIST) in 1998, arterial hypertension since 1998, and diabetes type 2 (DMT2) diagnosed a year ago adequately regulated with metformine only. On her physical exam, she did not have any signs of endocrinopathy, BMI was 25 kg/m², however cortisol was not suppressible in the overnight dexamethasone suppression test, followed by the same result in low dose dexamethasone test. Since she did not have any signs of hypercortisolemia except a relatively newly diagnosed DMT2, and absorption of orally ingested drugs was questionable, we decided to perform an IV overnight suppression test with 4 mg of dexamethasone which confirmed diagnosis of Cushing disease (cortisol 421 nmol/l). Other hormone test showed tireotropic and gonadotropic insufficiency. Transsphenoidal surgical removal of tumor was performed and control MRI showed no tumor residua while patohistological finding confirmed diagnosis of corticotropinoma.

Our patient presented with macroadenoma producing ACTH which are rare especially when presenting as silent macrocorticotropinomas. This is an educative example to keep in mind IV dexamethasone suppression test which could be easy and accurate tool in distinguishing patients with Cushing disease and pseudo-Cushing syndrome while at the same time avoiding the potential difficulties of drug compliance and absorption with oral dexamethasone.