Thyroid iodine uptake and serum triiodothyronine level in eldery subjects

Iodine uptake by the thyroid and serum triiodothyronine (T3) level in subjects aged from 65 to 93 years were determined. Low T3 level and normal uptake of inorganic iodine by the thyroid were found. In the light of these results it is suggested that normal accumulation of inorganic iodine and low production of T3 are characteristic features of euthyroidism in elderly subjects. It is believed that the function of the thyroid is expressed better by determination of the serum levels of thyroid hormones than determination of the uptake of radioactive iodine. Elaboration of standard normal values which would take into account abnormalities encountered in old age is postulated. (author)