Magnetic Resonance Imaging T2* Study of Pancreatic and Tissue Iron Overload and Glucose Dysregulation in Young Children with Transfusion Dependent Thalassemia

Abstract Background MRI has become the gold standard for monitoring somatic iron stores. It is assumed that there would be a latency time before pancreatic iron burden could give impaired glucose tolerance. The therapeutic window between clinically silent iron deposition and irreversible pancreatic damage is an appropriate timing for intensification of iron chelation and saving organ function Objective The primary objective of our study is to determine pancreatic, cardiac and hepatic iron overload using MRI T2* in patients with transfusion dependent thalassemia(TDT) and correlate it with type and dose of iron chelation and serum ferritin. The secondary objective is to correlate these findings and the effect on Beta cell function and glucose dysregulation. Subjects and Methods This was a cross sectional study of 50 patients with TDT, 30 (60%) males and 20 (40%) females, aged 7-16 years. Clinical data involved mainly; frequency of transfusion, history of splenectomy, iron chelation therapy and compliance on medications in addition to anthropometric measures and Tanner staging. Laboratory work up included mainly mean pre-transfusion Hb, serum ferritin, serum fructosamine, fasting glucose and insulin levels with calculation of (HOMA-B and HOMA-IR) and MRI T2* to assess Cardiac, liver and pancreatic MRI. Results The mean age was 9.8 ± 2.52 yrs. Almost 40% of adolescents had delayed puberty (Tanner stage 1) of the studied TDT patients, 48% were on Deferasirox, 6% on Deferiprone, 20% was on Deferasirox &Deferiprone and 18% were on Deferiprone & Deferoxamine and two thirds were compliant on iron chelation therapy. Almost 50% were on hydroxyurea. The mean serum ferritin was 2646.6 ± 2334.55ng/ml. 16% had mild hepatic iron overload, 20% had moderate hepatic iron overload while 8% only had severe hepatic iron overload. Regarding the cardiac MRI results, 96% of studied group had no evident cardiac iron overload while 4% had moderate cardiac iron overload and 8% had evidence of severe pancreatic iron overload. The mean fructosamine was 236±56.72, mean HOMA-IR value was 1.4±0.79(0.32-2.5) yet only 4 patients(8%) had HOMA-IR of ≥ 2.5 indicating mild insulin resistance. There was significant positive correlation between LIC(p0.028), fasting glucose(p0.050), insulin level(p > 0.001) and HOMA IR, positive correlation between T2*-weighted MRI pancreas and insulin level (p0.026) as well as positive correlation between mean serum ferritin and insulin level(p0.001),negative non-significant correlation(p0.455) between mean serum ferritin and cardiacMRIT2*. Conclusion In patients with TDT, pancreatic siderosis (late onset presentation) was correlated with hepatic T2*;but not with the cardiac T2* values. Glucose homeostasis and markers of insulin resistance were correlated to pancreatic and liver iron load. Glucose dysregulation may precedes evident pancreatic siderosis so strict iron chelation is essential to maintain B-cell function.