Natural history of thyroid function in ageing: an individual participant data analysis of 137 488 participants from 31 prospective cohort studies
Authors' conclusion
Ageing-related changes in thyroid function varied by sex and iodine status. Most individuals had stable thyroid function during ageing with a slight increase in TSH, although older adults displayed greater variability. Patterns of changing thyroid function were associated with an increased all-cause mortality risk, warranting further exploration of the underlying mechanisms and clinical management.
Study context
- Population
- Individuals aged ≥18 years in prospective population-based cohorts with thyroid function and mortality data, Europe, USA, Asia, Brazil and Australia; median age 60 years (range 18–106), 49.7% female
- Participants
- 137,488 individuals31 cohorts
- Exposure
- Patterns of changing thyroid function vs stable thyroid function
- Outcome
- All-cause mortality by pattern of thyroid function change
Methodological detailspopulation-based, cohort-stratified Cox models, linear mixed models stratified for sex and regional iodine status, Data collected between Jan 1, 2011, and Oct 13, 2022
- Population-based
- Cohort-stratified Cox models
- Linear mixed models stratified for sex and regional iodine status
- Data collected between Jan 1, 2011, and Oct 13, 2022
Main finding
As reported in the abstract
All-cause mortality
Hazard ratio (95% CI)
Increasing TSH with stable or decreasing FT4vs Stable
1.80(1.57–2.06)
Increasing TSH and increasing FT4vs Stable
2.45(2.01–2.97)
Decreasing TSH with decreasing FT4vs Stable
2.45(1.99–3.01)
Decreasing TSH with stable or increasing FT4vs Stable
1.94(1.68–2.24)
Observational data: associations, not effects.
Further findings
Increase in thyroid-stimulating hormone (TSH) from age 18 to 100 years, iodine-sufficient regions
mIU/L
- Female participants
- 0.61 (0.52 SD)
- Male participants
- 0.99 (0.76)
TSH and age
- Cross-sectionally, older age associated with higher TSH in iodine-sufficient and lower TSH in iodine-insufficient regions
- Longitudinally, TSH increased with age regardless of iodine status
- Greater variability in distribution and longitudinal TSH changes in adults aged ≥65 years
Free thyroxine (FT4) and age
- Higher FT4 with older age suggested cross-sectionally; longitudinally FT4 increased in iodine-sufficient and decreased in iodine-insufficient regions
Original publication
Natural history of thyroid function in ageing: an individual participant data analysis of 137 488 participants from 31 prospective cohort studies. Lancet Diabetes Endocrinol. Published 27 April 2026. doi:10.
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