[The effect of age on parameters of thyroid function]

The study was aimed at determination of the effect of age on the function of thyroid gland in all consecutive phases of human life--from the newborn period to the late senility. Blood serum concentrations of total and free thyroxine, total and free triiodothyronine, reverse--triiodothyronine and TSH were determined by radioimmunoassay in 1350 euthyroid persons of age ranging from 3 days to 81 years. It was found that both secretory function of the thyroid and the peripheral metabolism of the hormones secreted undergo the changes parallel to the advancement of age and to the development of the organism. The relation between the age and thyroid function is most clearly evident in the early period of life, i.e. between the newborn period and the time of attaining the maturity. In adults the relation is clearly less pronounced to gain in intensity again in elderly people.