- In middle-aged and older euthyroid individuals, those with low-normal thyroid function (i.e., highest tertile of thyroid-stimulating hormone [TSH] and lowest tertile of free thyroxine [FT4] reference ranges) are expected to live more years with and without non-communicable disease (NCD) than those with high-normal thyroid function (lowest tertile of TSH and highest tertile of FT4 reference ranges).
Why this matters
- Findings provide support for a re-evaluation of the reference ranges of thyroid function in middle-aged and older adults.
- Prospective population-based study of 7644 participants (mean age 64.5 years, 52.3% women) without known thyroid disease and with thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels within reference ranges.
- Total life expectancy (LE) and LE with and without NCD in TSH and FT4 tertiles were calculated in men and women.
- Funding: None.
- Over a median follow-up of 8 years (interquartile range, 2.7-9.9 years), 1396 incident NCD events and 1422 deaths were reported.
- Men and women in the highest vs lowest TSH tertile were expected to live 1.5 (95% CI, 0.8-2.3) and 1.5 (95% CI, 0.8-2.2) years longer (P<.001 for both respectively of which ci p=".002)" and years longer with ncd.>
- Difference in LE for men and women in the highest vs lowest FT4 tertile was −3.7 (95% CI, −5.1 to −2.2) and −3.3 (95% CI, −4.7 to −1.9) years (P<.001 for both respectively of which ci to and years without ncd.>
- Observational design.