Iron overload and glucose metabolism in subjects with β-thalassaemia major: an overview.

Thalassaemia is one of the most common genetic disorders caused by a reduction of the globin chains leading to chronic haemolytic anaemia from birth. The mainstay of treatment is blood transfusion to maintain adequate levels of the haemoglobin. Iron overload in β-thalassaemia major patients is secondary to multiple blood transfusions and increased iron absorption. Excess iron potentially catalyzes free-radicals generation and impairment in cellular function and integrity. Extensive iron-induced injury develops in the heart, liver, pancreas and endocrine system. Pancreatic iron loading in thalassaemia major patients begins at early childhood, and the prevalence of diabetes mellitus (DM) ranges from 6.4% to 14.1% in cross-sectional studies. Both insulin resistance and decreased insulin secretion contribute to DM in thalassaemia major patients. This has been shown by oral glucose tolerance test, euglycemic insulin clamp, homeostatic model assessment, intravenous glucose tolerance test and continuous glucose monitoring system. The prevalence of DM in thalassaemia has been shown to correlate with serum ferritin concentration, hepatitis C infection, and pancreatic and cardiac iron measured by imaging techniques. Therefore the incidence of disturbed glucose homeostasis depends on adherence to chelation treatment, the adequacy of the dosage, the chemical properties of the chelating agent and the prevention of liver infections.