Insulin resistance and beta cell function in chronically transfused patients of thalassemia major.

OBJECTIVE To assess the glycometabolic function in chronically transfused patients of beta- thalassemia major in terms of glucose tolerance, insulin secretion, insulin resistance index, and beta cell function index and to determine their relationship with clinical and biochemical profile. METHODS 30 homozygous thalassemia major children (aged 8-15 years) receiving regular blood transfusion and 10 age and sex matched normal children attending a tertiary level hospital were subjected to glucose tolerance test, estimation of fasting plasma insulin level, insulin resistance index and beta cell function index. Liver enzymes, liver size and indicators of iron overload (serum ferritin, total units of blood transfused, splenic size) were recorded. RESULTS There was no diabetes mellitus or impaired glucose tolerance test in either the cases or the controls. Fasting plasma insulin levels were significantly higher in cases than controls (P = 0.004), and correlated well with indicators of iron overload like total units of blood transfused (r = 0.41, P = 0.03), serum ferritin (r = 0.38, P = 0.038) and splenic size (r = 0.43, P = 0.03). Insulin resistance was higher in cases compared to controls (P = 0.01). It correlated well with age (r = 0.56, P = 0.006), fasting blood glucose (r = 0.8, P = 0.003), fasting plasma insulin (r = 0.95, P = 0.00001), total units of blood transfused (r = 0.52, P = 0.005), serum ferritin (r = 0.4, P = 0.02) and splenomegaly (r = 0.51, P = 0.004). Insulin resistance was higher in patients not on chelation therapy compared with those on chelation therapy (P = 0.003). The beta cell function index was higher in cases compared to the controls, but not of statistic significance (P = 0.077). It did not correlate well with total amount of blood transfused (r = -0.32, P = 0.08), serum ferritin (r = -0.138, P = 0.46), spleen size (r = 0.16, P = 0.36), or chelation therapy (P = 0.98). CONCLUSION Diabetes mellitus or impaired glucose was not seen in chronically transfused patients of thalassemia major (between 8 and 15 years of age), in our study. Insulin resistance, compensated by hyperinsulinemia, sets in early even before the onset of frank diabetes mellitus and correlated well with age, chelation therapy and indicators of iron overload like total units of blood transfused, splenomegaly and serum ferritin.