Assessment of thyroid functions and its role in body growth in thalassemia major

The present study was done to establish the role of thyroid gland in causing growth retardation in regularly transfused thalassemic children. Growth, skeletal maturation and thyroid functions were assessed in 25 patients of thalassemia major in the age range of 5-17 years (mean age 10.3 +/ 3.6 years). Thirteen patients were migrants from Pakistan and 12 were of Indian origin. Twenty-five age and sex matched children who were not anemic served as controls. Thalassemic children received multiple blood transfusions ranging from 36-350 units with a mean of 168.4 +/ 98.9 (+/ 1 SD). The mean pretransfusion hemoglobin was 8.7 +/ 1.6 g/dl. Twenty eight per cent patients were below the 5th percentile for height and another 24% between 5th and 10th percentiles. The height age retardation was more pronounced than bone age retardation. The mean serum total T3 and T4 levels were significantly lower (p < 0.001) and the mean serum TSH levels were significantly higher (p < 0.005) in patients with thalassemia major as compared to the controls. Eight patients had high TSH levels; of these 5 had compensated primary subclinical hypothyroidism (elevated TSH with normal T3 and T4) and 3 had uncompensated primary sub-clinical hypothyroidism (elevated TSH, low T4 and normal T3). Two patients had low T4 with normal T3 and TSH levels. Thyroid dysfunction was not related to age, sex, hemoglobin levels and country of origin but transfused iron load (units/kg, units/year) was significantly higher in patients with hypothyroid function compared to those with euthyroid function (p < 0.005). Height age, weight age and bone age retardations were more pronounced in patients with hypothyroid function; however, the difference was not statistically significant. It is concluded that hypothyroidism is unlikely to be the sole cause of growth retardation; however, it may have a potentiating or permissive role. The strong association of high transfused iron load and decreased thyroid function stresses the need for intensive chelation therapy.