Association between thyroid hormone sensitivity indices and renal function in community-dwelling euthyroid older...

Thyroid hormone sensitivity indices include thyroid feedback quantile-based index (TFQI), thyroid-stimulating hormone index (TSHI), and thyrotroph T4 resistance index (TT4RI), which assess central thyroid hormone sensitivity; however, their relationship with kidney function in euthyroid older adults is unclear. This cross-sectional study included 2,027 community-dwelling older adults (≥65 years) with euthyroid status in Shanghai, China. Serum TSH and FT4 were measured, and TFQI, TSHI, and TT4RI were calculated. Estimated glomerular filtration rate (eGFR) was determined using the Modification of Diet in Renal Disease (MDRD) equation. Associations between thyroid hormone sensitivity indices and eGFR were examined using multivariate linear and logistic regression models. Restricted cubic spline analysis was used to explore dose-response relationships. Subgroup analyses were also performed. Participants (mean age 71.8 ± 5.35 years; 48.7% male) had a 15.9% prevalence of reduced renal function. All three indices were higher in those with impaired renal function (p < 0.01). After adjustment, each index remained inversely associated with eGFR (coefficients preserved). TSHI and TT4RI remained significantly associated with reduced renal function (all p < 0.005), whereas TFQI showed a non-significant trend (p > 0.05). Spline analyses supported consistent inverse associations. Subgroup analyses supported consistent inverse associations. In conclusion, central thyroid hormone sensitivity indices are independently associated with lower renal function in euthyroid older adults.