Bone metabolism and mineral density in patients with beta-thalassemia major

OBJECTIVE: To evaluate bone metabolism in patients with beta-thalassemia major and to determine the factors associated with the development of osteoporosis.

METHODS: We studied 25 patients with thalassemia major with a mean age of 18.4 years (range 5-31) and aged and gender matched 24 healthy controls who were attending the outpatient physical medicine and rehabilitation clinic of Akdeniz University Hospital between January 2004 and March 2004 in Turkey. Bone mineral density (BMD) of lumbar spine (L1-L4) and proximal femur were determined using dual x-ray absorptiometry (DXA). Venous blood samples were obtained for determination of blood cell count and markers of bone formation and resorption.

RESULTS: The BMD values, both at lumbar and femoral neck levels were significantly lower in patients compared to controls. Serum N-telopeptide level was slightly higher, whereas osteocalcin was slightly lower in patients; however, these values were not statistically significant. Plasma levels of insulin like growth factor-1 (IGF-I) and insulin like growth factor binding protein-3 (IGFBP-3) were significantly lower in patients. Also, serum levels of estradiol and progesterone in females, luteinizing hormone and follicle-stimulating hormone in both gender were significantly lower in patients. Serum levels of free testosterone and total testosterone were lower in patients, but not statistically significant. Patients also had significantly higher serum phosphorus levels, and lower serum calcitonin levels compared to controls.

CONCLUSION: The BMD is decreased in thalassemic patients. Growth retardation, growth hormone / IGF-I / IGFBP-3 axis dysfunction, gonadal dysfunction and hypothalomo-pituitary-gonadal axis dysfunction may be responsible for the development of osteoporosis in the patients with beta-thalassemia major.