 - At the end of 3 month treatment, subjects will have a final visit, that is also scheduled to coincide with a routine transfusion visit. Subjects will have the same evaluation and procedures as in Baseline Visit : 1 a complete physical examination; 2 fasting laboratory evaluation that includes measurement of 25OHD, urinary calcium excretion and serum Calcium and PTH; and 3 Dietary calcium intake questionnaire. 