A Pathophysiological Study of Age-dependent Changes in Thyroid Function
1987 Volume 24 Issue 6 Pages 538-543
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1987 Volume 24 Issue 6 Pages 538-543
In order to investigate the effects of aging on thyroid function, total serum thyroxine (T4), triiodothyronine (T3), reverse T3 (rT3), free T4 (FT4) and thyrotropin (TSH) were measured in 109 normal controls, 153 cancer patients and 70 noncancerous inpatients. Mean T4, T3, T3/T4 and rT3 were stable throughout life in healthy adults. Values for TBG and FT4 in controls over age 70 were significantly lower than in younger controls. In cancer patients, mean serum T3 declined with increasing age, whereas throughout all decades, mean T4, rT3 and FT4 were stable. Concerning the age-related effect of undernutrition on thyroid frunction, cancer patients under age 60 had no significant correlation between serum values of T3, T3/T4, or rT3 and the magnitude of weight loss. However, reductions in serum T3 and T3/T4 and an elevation in serum rT3 values were noticed in lean cancer patients over age 60. In the effect of dementia on thyroid function, predementia and dementia group had significantly lower mean T3 and T3/T4 values than in sunormal or normal group, whereas mean T4, TBG and TSH values were stable. In noncancerous elderly inpatients, the group of grade 3 or 4 in performance state had a significant decrease in T3 and T3/T4. These findings suggest that age-related changes in extrathyroidal concersion from T4 to T3 reflect the multifactor including cancer itself, undernutrition, dementia and performance status.
