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Vitamin D and Osteopoirosis In the past, 200 IU of vitamin D was recommended daily for adults. The current daily recommendations are: 200 IU for individuals 19 to 50 years old, 400 IU for individuals 51 to 70 years old, and 600 IU for individuals over 71 years old. Under some conditions these amounts are inadequate. In one study, 700 to 800 IU were necessary to preserve bone density in older individuals.For individuals who have thalassemia major standard recommendations may not be adequate. A Greek study revealed that individuals who had transfusion dependent thalassemia and who were using desferoxamine for iron overload (these subjects had average serum ferritins greater than 3000 ng/ml) had low levels of vitamin D metabolites. It should be noted that it would appear that these patients were heavily iron overloaded and may have had decreased vitamin D metabolism secondary to compromised liver function. Osteoporosis is common in thalassemia major and can be modified by an adequate intake of calcium, vitamin D, and in hypogonadism hormone replacement. Individuals who have osteoporosis may require much higher doses of vitamin D to maintain or increase bone density, 800 to 1000 IU per day has been recommended by some experts. An Italian study of bone density in patients with thalassemia showed that only the most severe phenotype (bo/bo) had a decrease in bone density. However, a large daily intake of calcium and vitamin D could lead to hypercalciuria and hypercalcemia; supplementation at higher than recommended doses requires careful monitoring. All individuals who have thalassemia major should be monitored with bone density studies, serum 25-hydroxyvitamin D levels, parathyroid hormone levels, and evaluation for the development of hypogonadism. In some instances an assessment of bone turnover may be helpful. <page 1> <page 2> References: Chapuy MC, Arlot ME, Duboeuf F, et al. 'Vitamin D3 and calcium to prevent hip fracture in elderly women.' N Engl J Med 1992; 327:1637-42. Dawson-Hughes B, Harris SS, Krall EA, Dallal GE. 'Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age and older.' N Engl J Med 1997; 337:670-6. Filosa A, Di Maio S, et al. 'Longitudinal monitoring of bone mineral density in thalassemic patients, Genetic structure and osteoporosi.' Acta Paed 1997; 86:342-6. Moulas A, Challa A, et al. 'Vitamin D metabolites (25-hydroxyvitamin D, 24,25-dihydroxyvitamin D and 1,25-dihydroxyvitamin D) and osteocalcin in beta-thalassemia.' Acta Paed 1997; 86:594-9. Utiger RD. 'The need for more vitamin D.' N Engl J Med 1998; 338:828-9. |
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