Thyroid hormone indices in adult healthy subjects: no influence of aging

Controversy exists regarding the influence of aging on thyroid hormone metabolism. Several investigators report lowering of T3 and/or a rise in reverse T3 (rT3) in elderly subjects. Others suggest that these thyroid hormone alterations were secondary to associated disorders rather than old age, and questioned the "healthy" status of the subjects studied in the earlier reports. Therefore, to assess the possible effect of aging we studied T3 resin uptake, T4, free T4, T3, and rT3 concentrations in 152 euthyroid healthy adult subjects. These subjects were selected carefully and were therefore devoid of any illness, acute or chronic, and were not treated with any medications at the time of study. No significant alterations were noted in any of the thyroid hormone concentrations in subjects divided into groups according to age. Nor was there a significant difference in these parameters between men and women of any individual age group or for all ages combined. Therefore, old age per se may not influence thyroid hormone metabolism and hence may not induce changes in serum thyroid hormone concentrations. The changes in thyroid hormones noted previously in elderly subjects may be a reflection of concurrent disorders and not old age.