Study of Insulin Resistance in Patients With ß Thalassemia Major and Validity of Triglyceride Glucose (TYG) Index.

Complications like impaired glucose tolerance and diabetes mellitus due to iron overload need early identification in thalassemia. We studied the proportion of insulin resistance in thalassemia major patients on chronic transfusion, identified insulin resistance using homeostasis model assessment of insulin resistance (HOMA-IR) and triglyceride glucose (TYG) index, compared them and validated TYG index. In total, 73 thalassemia patients on regular transfusion for 3 years with serum ferritin >1500 ng/mL were studied. Serum ferritin, fasting blood glucose, triglycerides, and insulin levels were measured, HOMA-IR, and TYG index calculated and analyzed. Mean fasting glucose, triglyceride, and serum insulin values were 104 mg/dL, 164.18 mg/dL, and 19.6 m IU/mL, respectively. Mean serum ferritin was 5156 ng/mL. Insulin resistance was prevalent in one third of thalassemia patients and showed increase with age and serum ferritin. Insulin resistance by HOMA-IR was 32% as against 16% by TYG index with a cut-off value of 4.3. Using receiver operating charecteristic curve analysis, it was found that, by lowering the value of TYG index to 4.0215, sensitivity improved to 78.3% (from 39.13%) with specificity of 70%. Hence, we recommend a newer lower cut-off value of 4.0215 for TYG index for better sensitivity and specificity in identifying insulin resistance.

Nephropathic Cystinosis Presenting as Renal Fanconi Syndrome without Glycosuria.

Renal Fanconi syndrome is diagnosed by its cardinal features of glycosuria without diabetes, aminoaciduria, phosphaturia, and renal tubular acidosis. It is often associated with hypokalaemia, hypophosphatemia and rickets. We report a seven-year-old boy with nephropathic cystinosis who presented with all the cardinal features of renal Fanconi syndrome associated with rickets, pathological fractures, stage IV chronic kidney disease (CKD) and hypothyroidism. Slit-lamp examination of the cornea confirmed the diagnosis. However glycosuria was conspicuously absent. Whenever there are features of rickets with failure to thrive and recurrent vomiting renal rickets should be ruled out. Cystinosis is one such disorder and we report this case due its rarity and interesting clinical presentation.