Category: Pituitary Disorders/Neuroendocrinology
We present the case of a patient with aberrant response to high dose dexamethasone suppression test and other findings consistent with a possible ectopic ACTH syndrome that turned out to be Cushing’s disease.
Methods : n/a
Results : n/a
Case presentation:This is a 58-year-old female patient with rapid onset uncontrolled diabetes mellitus type 2, central obesity, easy bruising, abdominal striae and proximal muscle weakness who was screened for Cushing’s and had an abnormal high a 24 hour urine cortisol collection.1 mg dexamethasone suppression test (10 pm) cortisol level was 24.1 ug/dl with dexamethasone level 245 ng/dl (140-295 ng/dl) ACTH was 83.6 pg/ml (7.2-63 pg/ml). A high dose (8 mg) DST and cortisol level was 19.8 ug/dl with dexamethasone level 1040 ng/dl .She had a normal brain MRI.CT of the abdomen revealed cystic masses within the pancreas, measuring up to 1.5 cm.An EUS guided fine needle aspiration of the pancreatic masses showed an acellular specimen.An Ocreotide scan showed normal physiological distribution of the radiotracer activity throughout the body and no increase radiotracer activity in the previously described pancreatic cysts. Given these findings an IPSS was done. It confirmed a marked central to peripheral gradient. Repeat MRI of the brain showed a focus of relative hypo enhancement within the central pituitary gland that measures 7 x 4 x 9 mm.She underwent transphenoidal resection of pituitary gland and the pathology showed an adenoma positive for ACTH.Her post-operative course was uneventful, she was discharged on hydrocortisone, endocrine follow-up revealed normal levels of free t4, IGF 1 no evidence of DI, all her diabetes medication except metformin were discontinued due to optimal glucose control.
Discussion:Cushing’s disease usually manifests with signs and symptoms of hypercortisolemia with the onset being more insidious in pituitary Cushing’s as compared to the ectopic ACTH syndrome. A high dose dexamethasone suppression test usually distinguishes central vs. ectopic hypercortisolemia as this test proves the principle that that ACTH secretion by the pituitary adenomas that cause Cushing's disease is only relatively resistant to negative feedback regulation by glucocorticoids. However, this test does not correctly categorize every patient with ACTH-dependent Cushing's syndrome as the specificity of is less than 100 percent.
In order to distinguish the source of an ACTH dependent Cushing's syndrome,it is prudent to perform at least one test in addition to the dexamethasone suppression test, even in patients who meet current criteria for suppression especially with equivocal findings clinically or with imaging.
Associate Professor of Medicine
Albany Medical College
Delmar, New York
Dr.Sharma is an attending physician at the Albany Medical Center in Albany,New York.He sees patients with all endocrine disorders and has a special area of interest in management of thyroid disease and diabetes.
Albany Medical College
Dr.Kafrouni-Gerges is a second year fellow in the Division of Endocrinology at the Albany Medical College.