Adrenomedullin, a new peptide, in patients with insulinoma

Background: It has been demonstrated that adrenomedullin, a newly discovere d peptide, affects the release of insulin from pancreatic islets cells, sug gesting a role in the insulin-regulating system. Objective: To investigate whether adrenomedullin secretion is modified in p atients with insulin-secreting islet eel tumours, Design: The study was pet-formed in nine patients with surgically treated i nsulinoma, Circulating adrenomedullin was assayed using a specific radioimm unoassay and its localization and distribution in the tumour were determine d by means of immunohistochemistry. Results: Adrenomedullin concentrations were significantly greater in patien ts 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 adrenomedul lin decreased from 6.3 +/- 2.9 fmol/ml to 3.0 +/- 1.6 fmol/ml. Immunoreacti ve adrenomedullin was localized exclusively in the tumours cells, whereas s troma, surrounding pancreas parenchyma and major ducts were negative for th e peptide. Conclusions: Our findings indicate that circulating adrenomedullin is incre ased in insulinoma and that this increase is related to the neoplastic phen otype.