Vitamin D Insufficiency and Liver Iron Concentration in Transfusion Dependent Hemoglobinopathies in British Columbia

Patients with thalassemia major (TM) and other chronically transfused hereditary anemias are at increased risk of complications including endocrinopathies and bone disease due to iron overload. Vitamin D is important for bone health. Vitamin D deficiency is common in patients with transfusional iron overload, and the mechanism remains unclear. The first step in vitamin D metabolism, hydroxylation, occurs in the liver and liver iron overload may interfere with this step. This study investigates an association between degree of liver iron overload and vitamin D levels in patients with transfusion dependent hemoglobinopathies. Patients with TM, hemoglobin Eβ TM (Eβ TM), and congenital dyserythropiotc anemia (CDA) attending the Inherited Bleeding and Red Blood Cell Disorder Program in British Columbia (IBRBCD BC), Canada were identified. Included patients had an assessment of liver iron concentration (LIC) by MRI and endocrinology assessment including 25 hydroxy vitamin D level. Thirty patients were identified. The mean LIC was 5.13 mg/g dry weight (DW). Vitamin D deficiency/insufficiency was identified in 19 (63.3%). Eleven (36.7%) patients had an LIC ≥5 mg/gDW, 8 of whom had a vitamin D level 5 mg/gDW and vitamin D level <60nmol/L (P= 0.027) and there was a significant inverse correlation between LIC and vitamin D (R=-0.33). These results indicate an association between increased LIC and vitamin D insufficiency/deficiency, suggesting that liver iron overload may indeed affect vitamin D metabolism. Prospective trials are needed to confirm these results.