[TRH-TSH regulation in the aged and in patients with senile dementia]

TRH-TSH-thyroid regulation has been studied in clinically euthyroid elderly patients (average age 80 years) with senile dementia (27 women, 35 men) and normal controls (18 women, 10 men). TRH (40 mg) given by mouth did not stimulate TSH in one third of all subjects. Both sexes were equally affected. No relation to senile dementia or to goiter could be established. All groups, including the group without measurable TSH response (1 mE/1) showed an increase in peripheral thyroid hormone concentration after TRH. It is suggested that the low TSH response to TRH is a consequence of diminished pituitary responsiveness to TRH. Evaluation of thyroid function and diagnosis of hyperthyroidism in the elderly after TRH should be carried out with great caution.