Abnormal thyroid function and response to iodides in patients with cystic fibrosis.

It has been suggested that the development of goiter and hypothyroidism in 
patients receiving chronic iodide therapy indicates that they have underlying thyroid 
disease. In 1971, Dolan and Gibson, in a retrospective study, reviewed 
the records of children with cystic fibrosis receiving chronic expectorant therapy 
with iodide and reported that approximately 85 percent had goiter and 
15 percent suggestive clinical findings of hypothyroidism. This study, together with 
the fact that the thyroid, like lung and pancreas, is of 
endodermal origin raised the possibility that patients with cystic fibrosis might 
have an underlying defect in thyroid function. As thyroid function in 
patients with cystic fibrosis has not been evaluated in a systematic 
fashion, the present study was undertaken. In it, we have evaluated 
basal thyroid function in a large group of patients with cystic 
fibrosis and have, in addition, observed the effects of chronic iodide 
administration. The present study strongly suggests that there often occurs in 
patients with cystic fibrosis some derangement in thyroid hormone economy. The 
frequency with which iodides increased serum thyrotropin, decreased serum thyroxine concentration, 
and induced goiter, with or without hypothyroidism, in patients with cystic 
fibrosis, points strongly to the presence of an intrinsic abnormality of 
the thyroid in this disease. The nature of such abnormality remains 
unclear. 