Hepatic Hemosiderosis Contributes to Abnormal Vitamin D-PTH Axis in Thalassemia Major

The aim of this study was to evaluate the vitamin D-PTH axis in thalassemia major (TM) in relation to hepatic siderosis liver iron content.

In this case-controlled observational study, vitamin D-PTH axis was studied in 158 TM and 84 age and ethnicity-matched healthy nonthalassemic controls attending University College Hospital, London. Patients were classified as 25-hydroxy vitamin D (25-OHD) insufficient and sufficient if the value was less than or greater than 50 nmol/L, respectively. 25-OHD data were evaluated in relation to markers of iron load in TM.

In TM, 25-OHD insufficiency was 8-fold higher than the control group (odds ratio [OR], 8.1; 95% confidence interval [CI], 4.3-15.0; P<0.001). Similarly, serum PTH (P<0.001), calcium (P<0.001), and phosphate levels (P<0.05) were also significantly lower in TM compared with the controls. In TM, serum ferritin of >2500 μg/L (OR, 5.3; 95% CI, 2.3-12.3; P<0.01), liver iron of >7 mg/g dry weight (OR, 8.8; 95% CI, 3.5-10.3; P<0.001), and serum alanine aminotransferase of >50 IU/L (OR, 9.7; 95% CI, 4.0-23.5; P<0.001) were independent risk factors for low 25-OHD levels.

Our results suggest that TM had a 8-fold higher risk of 25-OHD insufficiency compared with the controls. This was likely to be associated with hepatic hemosiderosis.