Adrenomedullin, a new peptide, in patients with insulinoma

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. To investigate whether adrenomedullin secretion is modified in patients with insulin-secreting islet cell tumours. 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. 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. Our findings indicate that circulating adrenomedullin is increased in insulinoma and that this increase is related to the neoplastic phenotype.