Low TSH-response to TRH in a former endemic goiter area

During 30 yr of iodine prophylaxis endemic goiter in school children had disappeared in the Savonlinna area which has been the location of continuous surveillance in the East of Finland. In adults goiter is still found to some extent especially in older people. The iodine intake has increased from about 50 to 300 μg per day during these yr and the thyroidal uptake of radioactive iodine has decreased from over 60% to between 20 and 30%. However, there is a significant difference in this regard between nongoitrous individuals and goiter patients. In the present study comprising only goiter patients it was found that the thyroidal uptake was significantly higher in the group of patients with a subnormal response to TRH. These patients also had larger goiters and more palpable thyroid nodules than those with a normal response to TRH. The mean age was significantly higher (60.3 yr) as compared to that in the group which had a TSH-response to TRH of > 20 mU/l, smaller glands and less thyroid nodules (45.1 yr). The data fit well with the reports on increasing autonomy with increasing age in nontoxic goiter.