Pancreatic B-cell peptides as parameters for diagnosis and localisation of hormone secreting tumours.

Insulin, C-peptide and proinsulin were measured in peripheral blood of 11 patients suffering from different types of hormone-producing pancreatic B-cell tumours. While proinsulin was elevated in 10/11 patients during prolonged fasting, C-peptide and insulin levels were found within the reference range in 5/11 and 3/5 cases respectively. A rapid insulin assay performed during surgery was helpful for localisation and identification of the respective tumours.