EducationEndocrinologyPhysiologyAgingComparative EndocrinologyGerontologyThyroid DisordersThyroid EndocrinologyThyroid Hormone BiochemistrySerum Thyroid-stimulating Hormone MeasurementSubclinical HypothyroidismThyroid Function EvaluationThyroid Function TestsThyroid-stimulating Hormone TestingTriiodothyronine Measurement
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 (T<sub>4</sub>) and free T<sub>4</sub>(FT<sub>4</sub>) index, but only one had a low value for serum triiodothyronine (T<sub>3</sub>) or free T<sub>3</sub>(FT<sub>3</sub>) index. A further 14.4% had a slightly elevated level of serum TSH (>5≤10 μU/mL), but none had low values for serum T<sub>4</sub>or FT<sub>4</sub>index. Age alone has little effect on the measurements of T<sub>4</sub>; age is associated with slightly lower T<sub>3</sub>levels, 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. (<i>JAMA</i>242:247-250, 1979)