Abnormal glucose tolerance in beta-thalassemia patients: possible risk factors

ABSTRACT

In beta-thalassemia major, transfusional iron overload lead to impaired glucose tolerance [IGT] then diabetes mellitus [DM]. The pathogenetic mechanisms leading from siderosis to diabetes are still poorly understood. To assess the glycometabolic status in transfusion-dependent Egyptian beta-thalassemia patients and to evaluate the possible risk factors for abnormal glucose tolerance [AGT] in them. Oral glucose tolerance test [OGTT] was done to 54 multi-transfused thalassemic patients, aged 10.1-25.1 years, and 28 age-matched normal controls with measuring serum insulin level at 0, 120 minutes. Insulin sensitivity and insulin release index were calculated according to the homeostasis model assessment [HOMA], fasting insulin glucose ratio [FIG], insulin sensitivity index for glycemia [ISl gly] and fasting insulin resistance index [FIRI]. Indicator of iron overload and liver status were recorded. Thirteen patients [24.1%] were diagnosed to have variable degrees of AGT; either DM in 6 cases [11.1%] or IGT in 7 cases [13%] and normal glucose tolerance [NGT] was in 41 patients [75.9%]. Cases with AGT had significant higher mean postprandial insulin, FIRI and HOMA insulin resistance [IR], p=0.0001 for all, and significant lower mean HOMA beta-cell, p=0.007 if compared to the cases with NGT. By stepwise logistic regression analysis, the total blood taken per year was the independent risk factor for abnormal glucose tolerance, OR=0.49, p=0.03. Serum ferritin was higher in cases with AGT compared to cases with NGT, p= 0.04 and it correlated with fasting insulin level, FIRI and HOMA IR, p=0,003,0.001, 0.001 and r=0.4, 0.5, 0.5 respectively. Chronic hepatitis C was detected in 12 patients [92.3%] with AGT. Abnormal glucose tolerance is common in multi-transfused beta-thalassemia patients, which could be attributed to impaired beta-cell function, along with insulin resistance