Endocrine Abstracts

Identifying the cause of hypercortisolism is vital in ensuring the correct treatment plan for a patient. I present the case of a patient in whom the desmopressin test, as an adjunct to the CRH test, proved helpful in determining the cause. A 27 year old man who initially presented with weight gain, abdominal striae and sweating was admitted with low mood, anxiety and suicidal ideation. Tests showed elevated 24 hour urinary cortisol (highest 1446 nmol/24 hours), random cortisol (624 nmol/l) and ACTH (98 ng/l). Cortisol did not suppress after low dose dexamethasone suppression test (DST)(625 nmol/l). Cortisol suppressed by 60% to 259 nmol/lin high dose DST. MRI pituitary showed a 5mm adenoma and CT thorax, abdomen and pelvis was normal. He commenced on Metyrapone. There was a rise in cortisol and ACTH during CRH and desmopressin tests consistent with pituitary Cushing’s disease and he proceeded to transphenoidal surgery (TSS), achieving biochemical cure with day 2 morning cortisol of 46 nmol/l.

Discussion: It is imperative to identify the cause of ACTH dependent hypercortisolism before proceeding to TSS but this can be challenging as biochemical and imaging tests have limitations. MRI fails to identify a surgical target in up to 40% of patients with Cushing’s disease and may incorrectly implicate an incidentaloma. Bilateral inferior petrosal sinus sampling is more invasive, availability can be limited and success depends on surgical expertise. Methionine PET can effectively locate a corticotroph adenoma but is not yet widely available. The 2008 Endocrine Society Guideline advises confirming endogenous hypercortisolism with screening tests and then proceeding to CRH test but advised against using the desmopressin test until additional data validates it. Since then, research has established an adjunctive role of desmopressin testing in the diagnostic workup of ACTH dependent hypercortisolism. In the presented case, the combination of CRH and desmopressin tests, both consistent with pituitary Cushing’s disease provided the confidence with proceeding to TSS, resulting in cure. Given the recent announcement of a shortage of hCRH in the UK, the guidance around investigating hypercortisolism will be reviewed and more data on the desmopressin test could clarify its role.