Immunoreactive insulin in portal and hepatic venous blood in patients with insuloma.

The insulin level has been determined simultaneously in portal and hepatic venous blood in four patients with insuloma before and after administration of glucose and tolbutamide. Three patients displayed a higher insulin level in hepatic than in portal blood, although no hepatic metastases could be detected by radiologic examination. In contrast, portal insulin concentrations always exceeded hepatic in four control patients investigated in a similar way. The implications of these results are discussed.