Endocrine Abstracts

Ectopic Cushing’s syndrome (CS) is commonly caused by malignancy, often behaves aggressively and may not clinically manifest with features of hypercortisolism due to its rapid course and associated cachexia. This may mislead clinicians into discounting the diagnosis in patients with more indolent features of CS. We present a 41 year old woman with an 8 year history of Cushingoid features with associated hypertension, obesity and Type 2 Diabetes. Investigations confirmed CS with two elevated urinary free cortisol assessments (UFC) (934 and 906nmol/24hr respectively) and a failed overnight dexamethasone suppression test (221nmol/l). An ACTH of 39.1 ng/l confirmed ACTH-dependence and secondary hypothyroidism (TSH 1.68mIU/l, free T4 8.2pmol/l) suggested a pituitary source. Corticotrophin releasing hormone (CRH) testing was indeterminate with basal to peak increases of >50% for ACTH (24.1 to 86.5 ng/l) but <20% for cortisol (783 to 806 nmol/l). Subsequent contrast pituitary MRI showed a possible right sided microadenoma and metyrapone and thromboprophylaxis were started. Inferior petrosal sinus sampling (IPSS) favoured an ectopic source, with a central:peripheral ACTH ratio of <2 prior to CRH and <3 post CRH. A prolactin-normalised central:peripheral ACTH ratio of 0.4, also suggesting an ectopic source. An FDG-PET scan revealed a 12mm right maxillary sinus polyp with intense FDG avidity (SUVmax 11.9). This is consistent with a rare case of ectopic ACTH secretion from the paranasal sinuses and the patient has been referred for surgery. This case highlights the diagnostic challenge presented by CS, and emphasises the importance of thorough investigation to delineate ectopic and pituitary sources. It challenges the stereotype that ectopic CS always results from an aggressive malignant process and may instead present in a slowly progressive manner. It is essential that these cases are correctly diagnosed to avoid unnecessary surgery.