Association between thyroid hormone sensitivity indices and renal function in community-dwelling euthyroid older adults: a cross-sectional study

Abstract Background Thyroid hormone sensitivity indices such as the thyroid feedback quantile-based index (TFQI), TSH index (TSHI), and thyrotroph T4 resistance index (TT4RI) have been proposed to assess central thyroid hormone sensitivity. Their associations with kidney function in older adults with normal thyroid function remain unclear. Methods This cross-sectional study included 2,027 community older adults (≥ 65 years) with euthyroid status in Shanghai, China. Serum thyroid-stimulating hormone (TSH) and free thyroxine (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 multivariable linear and logistic regression models. Restricted cubic spline analysis was used to explore dose–response relationships. Subgroup analyses were also performed. Results Among all participants (71.8 ± 5.35 years; 48.7% male), 15.9% had reduced renal function (eGFR < 60 mL/min/1.73 m²). TFQI, TSHI, and TT4RI were significantly higher in participants with impaired renal function (all p < 0.01). After adjusting for demographic, lifestyle, and metabolic factors, all three indices remained inversely associated with eGFR in linear regression (TFQI: β = −2.646; TSHI: β = −2.924; TT4RI: β = −0.125; all p < 0.01). In logistic regression, TSHI and TT4RI remained significantly associated with reduced renal function (all p < 0.005), while TFQI showed a non trend (p > 0.05). Restricted cubic spline analyses revealed a linear inverse association between thyroid hormone sensitivity indices and eGFR. Subgroup analyses confirmed the robustness of these associations across different demographic and lifestyle strata. Conclusions Central thyroid hormone sensitivity indices were independently associated with decreased renal function in euthyroid older adults. This suggests that thyroid hormones central sensitivity is associated with the age-related decrease in renal function. Trial registration Not applicable.