Thyroid function in cystic fibrosis (CF) patients compared with healthy Israeli children

Abstract

In order to investigate whether the thyroid gland, an organ of endodermal origin, is affected in CF, thyroid metabolism was investigated in CF patients ranging in age from 1 to 20 years. Serum T4, T3, TSH, rT3 conc. as well as T3 in vitro uptake % were compared to the values elicited in a large group of healthy Israeli children in the same age range. The mean serum T4 conc. in CF patients (n=24) was 8.7±0.3 μg/dl (mean±SEM), and thus was not different from the mean of 8.8±0.1 in the normals (n=261). Serum T3 conc. were 170±7 ng/dl compared to 166±2 (n=213). The mean serum TSH (n=21) of 5.0±0.5 μU/ml and the mean T3 U% (n=12) of 25±0.9 were not different from the normals. However, the mean rT3 conc. of 44±8.6 ng/dl (n=12) was significantly (p<0.005) higher than the mean of 17±2.3 (n=20) in the normal children. There was no correlation between the percentile for weight or the severity of the disease as represented by the Shwachman score and the thyroid function. Conclusion: There is apparently no disturbance of the hypothalamic-pituitary-thyroid axis nor in the thyroid binding in the serum of CF patients. The peripheral conversion of T4 to T3 is normal. The increase in rT3 conc. in CF patients suggests that this is not due to malnutrition alone and might be due to chronic hypoxia.