Background and methods: We report a case of insulinoma in which the
diagnosis was very challenging as some of the biochemical data were consistently
equivocal. In order to assess the relative reliability of the analytical tests,
retrospective biochemical data on 45 other cases of histologically confirmed
insulinoma were evaluated, enabling the most secure diagnostic process to be
identified.
Results: The data showed that insulin concentrations alone, although
measurable, were equivocal in 17% of cases. The addition of C-peptide values
clarified the diagnosis in about 50% of the borderline cases, whilst ketone (β-hydroxybutyrate) concentrations were low during the
prevailing hypoglycaemia in all cases.
Conclusion: The combination of these three tests is suggested as the
most effective method for the biochemical diagnosis of hypoglycaemia due to
insulinoma.
