John Newell-Price, University of Sheffield, UK

Differential diagnosis of Cushing's disease is challenging, as patients typically experience a range of related disorders at presentation and may exhibit non-specific symptoms.

Pseudo-Cushing's is common and the presence of cyclical Cushing's disease or the absence of a visible pituitary adenoma on MRI can confound diagnosis.

Multiple tests are required to confirm the diagnosis of Cushing's disease, including 24-hour UFC, late-night salivary cortisol and dexamethasone suppression tests. Once endogenous Cushing's syndrome is confirmed, the cause of the excess cortisol secretion needs to be determined, i.e. pituitary, ectopic ACTH production or adrenal. A pituitary adenoma is generally confirmed with a combination of tests that may include MRI, inferior petrosal sinus sampling and the high-dose dexamethasone suppression test.

The primary treatment choice for Cushing's disease is surgery. Early hypocortisolaemia is a good prognostic indicator for remission and long term remission is achieved in around 60-70% of patients. The definition of remission is no signs or symptoms and normal biochemistry of the HPA axis on long term follow up. However, partial remission can occur in a some patients and is the most challenging scenario with regards to follow up management.  Reoperation, medical therapy and pituitary radiotherapy plus medical therapy are the main options for these patients.