Combined vitamin D parathyroid defect in thalassemia major.

A 17-year-old girl with thalassemia major experienced tetany. The serum calcium level was 5.5 mg/dL, and the phosphorus level was 6.3 mg/dL. Serum levels of parathyroid hormone (PTH) and 25-hydroxyvitamin D (25-OHD) were subnormal at 125 pg/mL and 8.1 ng/mL, respectively, As a result of these findings, serum 25-OHD and PTH levels were measured in an additional 12 patients with thalassemia major. Low levels of both 25-OHD and PTH were found frequently. An increase in serum 25-OHD levels was noted in each of four patients who were examined after iron chelation therapy.