Thyroid function in children after allogeneic bone marrow transplantation.

Thyroid function was investigated in 35 children after allogeneic BMT. The study was longitudinal and all patients were followed for at least 5 years. Once a year TSH, T4, T3 and the TRH test were performed. Patients with severe aplastic anemia (n = 6) were transplanted without total body irradiation (TBI) and they had no detectable alterations in thyroid function. Patients with leukemia (n = 27) were conditioned with 10 Gy TBI in one fraction. The accumulated frequencies of thyroid dysfunction were 3 of 27 (11%) with high TSH and low T3 or T4 levels, and 10 of 27 (37%) with high basal TSH and normal T3 and T4 levels. An additional 11 of 27 (41%) had an exaggerated TSH response in the TRH test and normal basal TSH and T3/T4 levels. Only 3 of 27 (11%) continued to have normal values. Treatment with levo-thyroxine (L-T4) was given to the patients with a high basal TSH level. As 24 of 27 (89%) children had signs of disturbance in the thyroid axis, prophylactic L-T4 treatment for a few years after BMT with TBI may be of value. The main cause of a change in thyroid function after BMT seems to be conditioning with TBI.