PURPOSE: The study aims to investigate the relationship between thyroid-stimulating hormone (TSH) and remnant cholesterol (RC) in euthyroid adults. METHODS: The adults who were recruited for the study had undergone physical examination at Beijing Chao-Yang Hospital. High RC levels were defined as the upper quartile of RC levels in males and females, respectively. The relationship between TSH and RC was assessed using the logistic and linear regression models. RESULTS: A total of 29,708 adults (14,347 males and 15,361 females) were enrolled in this study. RC ≥ 0.77 mmol/L in males and RC ≥ 0.60 mmol/L in females were defined as high RC levels. With increasing serum TSH levels, the percentage of adults with high RC levels increased. The odds ratios (ORs (95% confidence intervals (CIs)) for high RC levels increased as TSH quartiles (Q) rose after full adjustments [males: Q2 1.11 (1.00-1.24), P <
0.05
Q3 1.03 (0.92-1.15), P >
0.05
Q4 1.25 (1.12-1.40), P <
0.001
and females: Q2 1.07 (0.96-1.20), P >
0.05
Q3 1.17 (1.05-1.31), P <
0.01, Q4 1.33 (1.20-1.48), P <
0.001, all P for trend <
0.001], using Q1 as the reference. CONCLUSION: Higher TSH levels were independently associated with higher RC levels in euthyroid adults, this underscoring the significance of regulating TSH levels appropriately.