Adrenomedullin, a new peptide, in patients with insulinoma

BACKGROUND: It has been demonstrated that adrenomedullin, a newly discovered peptide, affects the release of insulin from pancreatic islets cells, suggesting a role in the insulin-regulating system. OBJECTIVE: To investigate whether adrenomedullin secretion is modified in patients with insulin-secreting islet cell tumours. DESIGN: The study was performed in nine patients with surgically treated insulinoma. Circulating adrenomedullin was assayed using a specific radioimmunoassay and its localization and distribution in the tumour were determined by means of immunohistochemistry. RESULTS: Adrenomedullin concentrations were significantly greater in patients with insulinoma (6.6 +/- 3.2 fmol/ml) than in controls (2.1 +/- 1.1 fmol/ml). In six patients monitored before and after surgery, plasma adrenomedullin decreased from 6.3 +/- 2.9 fmol/ml to 3.0 +/- 1.6 fmol/ml. Immunoreactive adrenomedullin was localized exclusively in the tumours cells, whereas stroma, surrounding pancreas parenchyma and major ducts were negative for the peptide. CONCLUSIONS: Our findings indicate that circulating adrenomedullin is increased in insulinoma and that this increase is related to the neoplastic phenotype.