The Aging Thyroid

Of 344 relatively healthy persons older than 60 years, 22 (5.9%) had a clearly elevated level of serum thyrotropin (TSH) (>10 μU/mL), a finding more common in women than in men. Ten of the 22 had low values for serum thyroxine (T₄) and free T₄(FT₄) index, but only one had a low value for serum triiodothyronine (T₃) or free T₃(FT₃) index. A further 14.4% had a slightly elevated level of serum TSH (>5≤10 μU/mL), but none had low values for serum T₄or FT₄index. Age alone has little effect on the measurements of T₄; age is associated with slightly lower T₃levels, but only in men 60 years or older or in women 80 years or older. Longitudinal studies should determine if a slightly elevated serum TSH rises further with age and if there is a causal relationship between a high level of serum TSH and cardiovascular disease. (JAMA242:247-250, 1979)