Background: several studies suggest that a decreased thyroid activity might be favourable in oldest-old subjects and that subclinical thyroid hyperfunction may be detrimental.
Objectives: to verify whether declining levels of circulating thyroid hormones may contribute to longevity.
Design: cross-sectional observational study.
Setting: all subjects were born in Calabria (southern Italy) and their ancestry in the region was ascertained up to the grandparents.
Subjects: six hundred and four home-dwelling subjects (301 females, 303 males), divided into three groups: 278 individuals 60-85 years old; 179 children or nieces/nephews of centenarians who are 60-85 years old; 147 individuals older than 85 years.
Methods: thyroid function parameters were measured in the frame of a comprehensive geriatric assessment.
Results: FT3 and FT4 levels were negatively associated with age. Lower levels of FT3, FT4 and TSH were found in centenarians' children and nieces/nephews with respect to age-matched controls. Indeed, being a relative of centenarians qualified as an independent correlate of thyroid parameters.
Conclusions: age-related subtle thyroid hypofunction (either due to a familial component or due to a reset of the thyroid function occurring between the sixth and the eighth decade of life) appears to be related to longevity.