Glucose Intolerance and Diabetes in Thalassaemia major

Abstract

The management of homozygous β-thalassaemia involves regular blood transfusions and subcutaneous infusions of the iron-chelating agent desferrioxamine (DFX) [1]. This optimal treatment appears to ensure good health in the long term, if DFX chelation begins in early childhood and is complied with, and if there is no evidence of viral hepatitis, then the patients can be expected to survive for an indefinite duration. Most of the complications of thalassaemia major are attributable to transfusion-transmitted viruses causing liver disease and to iron overload. The latter may be the result of economic circumstance, late onset of iron-chelation therapy or poor compliance with DFX treatment. In iron overload the excess iron which is deposited in the tissues causes damage. The mechanisms by which iron damages the organs have only recently been identified [2]. Toxicity begins when the iron load in a particular tissue exceeds the tissue or blood binding capacity of iron, and large quantities of free nontransferrin iron appear. This “free iron” is a catalyst of the production of oxygen species that damage cells and peroxidize membrane lipids, leading to cell destruction. The liver has a large capacity for producing proteins which bind the iron and store it in the form of ferritin and haemosiderin. However, eventually cirrhosis develops, which may be accelerated by chronic hepatits B or C viruses. In the pancreas iron deposition in the interstitial cells results in excessive collagen deposition and defective microcirculation. Impaired oxygen supply eventually leads to insulin deficiency [3]. This greatly contributes to the multifactorial pathology of the development of glucose intolerance and diabetes in thalassaemia major (Fig. 1).