Bone Abstracts

Objective: Transfusion dependent thalassemia (TM) patients have routinely been placed on vitamin D supplementation due to their increased risk of osteoporosis, as well as their high rates of vitamin D deficiency (serum 25 hydroxyvitamin D (25-OHD) <11 ng/ml) and insufficiency (25-OHD <30 ng/ml). Furthermore, recent studies have linked 25-OHD levels to hypercalciuria and nephrolithiasis in TM. The objective of this study is to determine the effect of vitamin D supplementation on vitamin D stores and calcium excretion in TM patients.

Methods: Prospective, single-blind, placebo-controlled study of TM patients followed in the transfusion clinic at Weill Cornell/New York Presbyterian Hospital. Patients with 25-OHD concentrations between 15 and 29 ng/ml were eligible for this 3-month study. Subjects were assigned in a block type of enrollment to the ‘high dose’ (2,000 IU of vitamin D/day) group vs placebo group.

Results: Twenty subjects were evaluated, with 10 assigned to each group. The ‘high dose’ group consisted of seven females/three males, aged 14.6–45.7 years. The placebo group consisted of five females/five males, aged 15.2–45.5 years.

After the 3 month study period, hypercalciuria developed more frequently in those treated in the ‘high dose’ group. In the placebo group, the average 25-OHD level did not change significantly (baseline: 17.6 ng/ml, 3 month 17.0 ng/ml, P=0.65). 2/10 (20.0%) and 0/5 (0%) developed hypercalciuria or had worsening hypercalciuria, based on spot urine calcium/creatinine and 24 h urine calcium excretion, respectively. In the ‘high dose’ group, the average 25-OHD level increased from 20.1 to 31.9 ng/ml (P<0.01). 5/10 (50.0%) and 3/7 (42.8%) developed hypercalciuria or had worsening hypercalciuria, based on spot urine calcium/creatinine and 24 h urine calcium excretion, respectively.

Conclusion: Our findings suggest that ‘high dose’ vitamin D supplementation results in high rates of hypercalciuria in TM patients. Further studies are necessary to determine the optimal dose of vitamin D supplementation and ideal 25-OHD level to minimize the risk of osteoporosis while preventing nephrolithiasis in TM patients.