Ectopic ACTH syndrome: our experience with 25 cases

Luiz Roberto Salgado, Maria Candida B Villares Fragoso, Mirta Knoepfelmacher, Marcio Carlos Machado, Sorahia Domenice, Maria Adelaide Albergaria Pereira and Berenice Biharinho de Mendonça. Ectopic adrenocorticotrophic hormone (ACTH) syndrome (EAS) is seen in between 5 and 10% of patients with ACTH-dependent hypercortisolism. Caused by excessive ACTH secretion and malignant intrathoracic tumours, its characteristics include; proximal myopathy, hypokalaemia, hyperpigmentaion and glucose intolerance. Hypokalaemia is often a distinguishing feature of EAS, being more common in this syndrome than in another similar disorder – Cushing’s disease. The differentiation between EAS and Cushing’s disease is difficult and requires accurate tests to make a correct diagnosis. Here, Salgado and colleagues assess the accuracy of dynamic tests and imaging techniques currently used to diagnose EAS. Their findings suggest that, of several dynamic tests, which alter levels of cortisol or corticotrophin-releasing hormone in Cushing’s disease but not EAS, inferior petrosal sinus sampling (IPSS) using desmopressin is the most accurate and considered the ‘gold standard’. Of the imaging techniques assessed, CT was considered more accurate at locating tumours than MRI, although both were effective. Positron emission tomography with fluorodeoxyglucose and scintigraphy with somatostatin analogue were also found to be relatively effective in detecting the location of occult tumours missed by CT and MRI. In conclusion, IPSS, together with less invasive dynamic tests is effective correctly diagnosing EAS in most cases, and imaging can locate the tumours at the source of the hormonal imbalance. However, many tumours still cannot be located using these existing techniques. EJE 155-5 735–743