Relationship Between Circulating Thyroid-Stimulating Hormone, Free Thyroxine, and Free Triiodothyronine Concentrations and 9-Year Mortality in Euthyroid Elderly Adults - American Geriatric Society

Objectives

To determine the association between plasma thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) levels and all-cause mortality in older adults who had levels of all three hormones in the normal range.

Design

Longitudinal.

Setting

Community-based.

Participants

Euthyroid Invecchiare in Chianti study participants aged 65 and older (N = 815).

Measurements

Plasma TSH, FT3, and FT4 levels were predictors, and 9-year all-cause mortality was the outcome. Cox proportional hazards models adjusted for confounders were used to examine the relationship between TSH, FT3, and FT4 quartiles and all-cause mortality over 9 years of follow-up.

Results

During follow-up (mean person-years 8,643.7, range 35.4–16,985.0), 181 deaths occurred (22.2%). Participants with TSH in the lowest quartile had higher mortality than the rest of the population. After adjusting for multiple confounders, participants with TSH in the lowest quartile (hazard ratio = 2.22, 95% confidence interval = 1.19–4.22) had significantly higher all-cause mortality than those with TSH in the highest quartile. Neither FT3 nor FT4 was associated with mortality.

Conclusion

In elderly euthyroid subjects, normal-low TSH is an independent risk factor for all-cause mortality.

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