Carbohydrate metabolism in porphyria

Abstract

A high proportion of patients with porphyria cutanea tarda (PCT) show a hyperinsulinemic response to the oral glucose tolerance test (OGTT) attributed to the hepatopathy also frequent in this disease. We propose that hyperinsulinemia is the main feature and source of carbohydrate metabolic alterations present in both chronic and acute types of porphyria. In order to verify this hypothesis, the insulinemic response to the OGTT was studied in 12 healthy controls, 18 PCT patients and 14 patients with acute types of porphyria. Of the PCT patients, 22% showed an altered response to the OGTT, in agreement with other authors. The frequency of altered hyperinsulinemic response in PCT patients was similar to that in acute-type porphyria patients. However, the intensity of this alteration was significantly higher in PCT than in acute-type porphyria patients. Among the PCT patients with hyperinsulinemic response, some showed evidence of hepatic damage, while others did not. On the other hand, patients with acute types of porphyria and chronic hepatic damage, demonstrated by histology procedures, did not show the hyperinsulinemic phenomenon. In summary, both PCT and acute-type porphyria patients show a higher frequency of hyperinsulinemic response to the OGTT than the general population. This hyperinsulinemic response cannot be attributed to concomitant hepatic damage, but hepatopathy can intensify the insulinemic response.