Sex Differences in the Association Between Thyroid Hormone Sensitivity and Cardiovascular-Kidney-Metabolic Syndrome.

Background: The relationship between thyroid hormone sensitivity and cardiovascular-kidney-metabolic (CKM) syndrome remains unclear. This study aims to investigate the association between thyroid hormone sensitivity and the early-stage of CKM syndrome, with a specific focus on the moderating effects of sex and age.

Methods: A total of 8,391 euthyroid participants were enrolled in this cross-sectional study. Data on metabolic parameters and thyroid hormone levels were collected. Thyroid hormone sensitivity indices-thyroid feedback quantile index (TFQI), thyroid-stimulating hormone index (TSHI), TT4 resistance index (TT4RI), and free thyroxine to free triiodothyronine ratio were calculated. Logistic regression models and restricted cubic spline regression (RCS) were used to analyze the association between thyroid hormone sensitivity and stage 2 of CKM syndrome stratified by sex and age.

Results: In men, the higher TFQI, TSHI, and TT4RI values were significantly associated with increased risks of stage 2 of CKM. In women, these associations were weaker but still present, particularly for TSHI. RCS analysis also showed that the risk of CKM tended to increase with decreasing thyroid hormone sensitivity in men. However, these associations in women were not as significant as in men. Age-stratified analysis revealed that older men (>50 years) showed a stronger correlation between thyroid hormone sensitivity and CKM syndrome compared to women.

Conclusion: This study demonstrated that impaired thyroid hormone sensitivity is significantly associated with the early-stage of CKM syndrome, particularly in older men. These findings provide the evidence of the importance of thyroid hormone sensitivity in CKM syndrome, especially in men over the age of 50.