[A 64-year-old female patient with recurring hypoglycaemia. Difficult aspects of diagnosis].

Insulinomas are the most common pancreatic islet cell tumours and are characterised by uncontrolled insulin secretion even in the presence of hypoglycaemia. Diagnosis is usually made by the detection of endogenous hyperinsulinism over a period of fasting. We report the case of a patient with insulinoma without hyperinsulinaemia. A secretion and overexpression of split insulin has to be discussed. The diagnosis was made by endoscopic ultrasound-guided fine-needle aspiration and the immunohistochemical detection of chromogranine. In conclusion, the present report demonstrates that insulinomas should be considered and searched for in every case of hypoglycaemia, even when associated with normal insulin levels. It also confirms the essential role of endoscopic ultrasonography in the diagnosis of insulin-secreting tumors.