Endocrine Abstracts

Diagnosis of Cushing’s disease can be a difficult and lengthy process with repeated and dynamic testing required to ensure the correct diagnosis is made prior to invasive intervention such as surgery. This case demonstrates that even with meticulous investigation the underlying cause of the disease can still be evasive. A 43-year-old female presented with a history of hypertension since age 20, managed with Amlodipine (10 mg) and Ramipril (10 mg). She was investigated for secondary causes and an overnight Dexamethasone Suppression Test (DST) revealed a raised cortisol of 168nmol/lwhich was supported by a 24-hour urinary free cortisol result of 398nmol/24hour (normal <199nmol/24hour). A low dose DST found baseline cortisol 320nmol/lwith ACTH 40ng/lwith cortisol falling to 95nmol/lat 48 hours. The remainder of her pituitary function testing was normal. An MRI pituitary noted a 10x13mm enhancing lesion in keeping with a right sided pituitary macroadenoma. On review at the tertiary centre she presented with lethargy and decreased motivation and was noted to have facial plethora and fullness with central adiposity and thin skin. She was felt to have ACTH dependant Cushing’s syndrome with a proven pituitary macroadenoma which was the probable source. Further confirmatory testing for Cushing’s disease was carried out with a CRH test finding a tripling of ACTH at 30minutes (41ng/l- 122ng/l), and an almost doubling of cortisol at 45minutes (454nmol/l- 771nmol/l). A CT-CAP showed no other potential sources of ectopic ACTH. The patient was commenced on Metyrapone (250 mg BD) and VTE prophylaxis with low molecular weight heparin pending surgery. Following trans-sphenoidal surgery, histology found the adenoma to be a Gonadotrophinoma. Macroscopically no other lesions had been seen in the pituitary gland. Post-surgery the patient remained symptomatic, with a cortisol of 329nmol/lpost overnight DST (ACTH 42ng/l). Inferior Petrosal Sinus Sampling (IPSS) with CRH stimulation revealed a baseline peripheral ACTH of 39ng/l(157ng/lat 15minutes), right sided IPSS ACTH at baseline 984ng/l(1650ng/lat 15minutes) and left sided IPSS ACTH at baseline 558ng/lrising at 5minutes to >2000ng/l(greater than upper limit of detection thereafter). This indicates Cushing’s disease possibly from a left sided pituitary adenoma. A repeat MRI pituitary has found 2 areas of reduced enhancement which could be residual or another adenoma. The patient remains on Metyrapone, and Apixaban for VTE prophylaxis and is awaiting a Methionine PET scan and genetic testing for MEN1.