Case Report: The Curious Case of Misleading Cortisol


Luke Flower, Sogha Khawari, Imperial College Healthcare NHS Trust


A 73 year old female presented to our endocrinology ward having been admitted with hyperglycaemia and ketosis, discovered when attending hospital for a PET scan to investigate a right-sided adrenal mass.


A Short Synacthen Test was performed prior to this admission, following initial discovery of adrenal mass, demonstrating a consistently raised cortisol. This, in combination with her poorly controlled diabetes, was suggestive of a cushingoid picture.


On admission to our hospital, she was found to have a raised cortisol of 667. Her past medical history included a known right adrenal mass with IVC thrombus, osteoporosis and previous rectal prolapse repair.


During this admission, a large mass was found on CXR in the mid-zone of her left lung. After CT and lung MDT, it was concluded that the mass was likely a primary lung cancer in the lower left lobe and the right adrenal abnormality represents a metastatic deposit.  It was thought that a lung malignancy may have been producing ectopic ACTH and resulting in a cushingoid picture. ACTH immunohistochemistry was performed on the lung mass biopsy, however this was negative.


A low dose dexamethasone suppression test was performed to help confirm a diagnosis of Cushing's syndrome. The results were: initial ACTH 59.8 and cortisol 537, at 24 hours ACTH 8.0 and cortisol 75, at 48 hours ACTH 6.3 and cortisol 56. This demonstrated a suppressed cortisol, in keeping with a normal physiological response - making Cushing's syndrome unlikely.


In conclusion, following an initial raised morning cortisol and an adrenal mass there was a high suspicion of Cushing's syndrome. Following more specific investigations it was demonstrated that this cortisol may have been a misleading result and this diagnosis was in fact unlikely. In retrospect the raised cortisol may have been stress related due to illness, multiple recent hospital admissions and her new diagnoses. This highlights the clinical importance of utilising specific investigations and keeping an open diagnostic mind.