Cystic fibrosis: thyroid function and alpha fetoprotein [letter].

Our recent studies showed normal serum thyroxine but lower serum total and 
free tri-iodothyronine and higher serum thyrotropin concentration in children with cystic 
fibrosis than in controls matched for age and sex. Furthermore, administration 
of iodides to children with cystic fibrosis resulted in goiter decrease 
in serum thyroxine and increase in serum thyrotropin concentration. Our studies 
point to multiple derangement in thyroid hormone economy in children with 
cystic fibrosis. Peripheral deiodination of thyroxine to tri-iodothyronine may be defective, 
probably as a result of a state of malnutrition. An intrinsic 
abnormality may also be present in the thyroid gland. Iodide, which 
is frequently used in this disease, may enhance this defect, occasionally 
producing hypothyroidism. Therefore, the thyroid, like other organs of endodermal origin 
(lung and pancreas), may be involved in cystic fibrosis. Thyroid function 
should be examined in all children with cystic fibrosis, and if 
iodides are administered, replacement doses of thyroid hormones should also be 
given to prevent hypothyroidism. - A recent review of cystic fibrosis 
referred to the report by Chandra et al. that the serum 
level of alpha fetoprotein (AFP) is increased in patients with cystic 
fibrosis (CF) or heterozygotes who bear the CF gene. The report 
of Chandra et al. had prompted us to assess the level 
of AFP in cystic fibrosis, and we wish to record here 
briefly our negative observations. On the whole, these results suggest that 
AFP is not increased in cystic fibrosis. - We thought that 
the complications of therapy with iodides or other agents was beyond 
the scope of our review, and thus we did not discuss 
the very interesting observations of the high rate of goiter after 
iodide therapy in CF patients. Whether this phenomenon indicates a subclinical 
thyroid defect related to CF per se or is a secondary 
effect of chronic illness in youth is still unsettled. 