BACKGROUND: The association of thyroid hormone sensitivity with heart rate remains unclear. OBJECTIVE: This study aims to elucidate the relationship between impaired thyroid hormone sensitivity and lower heart rate in the euthyroid population. METHODS: A total of 550 participants were included. Heart rate and serum biochemicals were measured. Thyroid hormone sensitivity indices were calculated by TSH index (TSHI), thyrotropin thyroxine resistance index (TT4RI), thyroid feedback quantile-based index (TFQI), Chinese-referenced parametric TFQI (PTFQI) and the ratio of FT3 to FT4 (FT3/FT4). Logistic regression analyses were applied to explore the relationship between indices of thyroid hormone sensitivity and heart rate. RESULTS: TSHI, TT4RI, TFQI, PTFQI were higher, and FT3/FT4 was lower in participants with heart rates ≤ 60bmp (all P <
0.001). Subjects with increased TSHI, TT4RI, TFQI, PTFQI and reduced FT3/FT4 had lower heart rates (≤60bmp) (all P for trend <
0.001). Odds ratios (ORs) (95% confidence intervals [CIs]) for TSHI, TT4RI, TFQI, PTFQI and FT3/FT4 in the highest quartile were respectively 2.090 (1.092-4.000), 2.240 (1.151-4.361), 2.014 (1.043-3.887), 2.163 (1.123-4.166) and 0.498, (0.249-0.996) compared with the lowest quartile after adjusted for gender, age, body mass index (BMI), smoking, drinking, hypertension, diabetes, coronary artery disease, glycated hemoglobin, total cholesterol, low-density lipoprotein, triglycerides. CONCLUSION: Impaired sensitivity to thyroid hormones was associated with lower heart rate in euthyroid subjects. Future large-scale studies are needed to confirm our findings.