Thyroid nodules are prevalent endocrine disorders, with their detection rates rising significantly. Recent data indicate that about 20.4% of adults may have thyroid nodules, with malignancy rates between 8% and 16%. Factors contributing to their occurrence include sex, age, genetic predispositions, and iodine nutritional status. Emerging evidence also points to metabolic abnormalities as influencing both the presence and severity of thyroid nodules. In particular, insulin resistance (IR), a core component of metabolic syndrome, has been linked to an increased likelihood of developing thyroid nodules even after adjusting for traditional risk factors. This study seeks to extend existing research by examining the associations of the Metabolic Score for Insulin Resistance (METS-IR) and elevated uric acid (UA) levels with prevalent thyroid nodules.
The study analyzed 5,232 individuals who underwent health examinations at the Health Management Center of the First Hospital of Shanxi Medical University from January 2018 to December 2021. Of these, 38% were male and 62% were female. Participants were selected based on strict inclusion and exclusion criteria, ensuring that only individuals aged 18 years or older with no history of thyroid issues or severe organic diseases were included in the analysis.
Data was collected meticulously, covering demographics, medical history, medication use, and anthropometric measurements performed by trained nurses. Key biochemical markers, including fasting plasma glucose and UA, were assessed after participants underwent overnight fasting. Thyroid ultrasonography was performed by qualified sonographers, with nodules categorized according to the Chinese Thyroid Imaging Reporting and Data System (C-TIRADS). The METS-IR was computed using a specific formula incorporating FPG, triglycerides, HDL cholesterol, and BMI. Participants were categorized into quartiles based on their METS-IR and UA levels for analytical purposes.
The analysis revealed that individuals with the highest quartiles of METS-IR and UA had significantly greater odds of thyroid nodules compared to those in lower quartiles. Specifically, the effect estimates indicated an odds ratio (OR) of 3.928 for METS-IR and 3.627 for UA, both with a 95% confidence interval indicating high statistical significance (P < 0.001). The study employed multivariable logistic regression, along with restricted cubic spline regression to investigate nonlinear relationships across specific C-TIRADS categories. In these analyses, the associations remained robust across various subgroup analyses, emphasizing that higher levels of METS-IR and UA were consistently linked to a higher prevalence of thyroid nodules.
Furthermore, while SBP was hypothesized to mediate the observed associations, the exploratory analyses indicated only limited and outcome-dependent mediation effects, particularly noting that METS-IR accounted for 6.62% while UA contributed 1.44% in the overall sample. However, the mediation effect varied across C-TIRADS categories, indicating complex relationships where direct associations were stronger in C-TIRADS 4 nodules compared to lower-risk categories.
These findings highlight the importance of metabolic dysfunctions associated with insulin resistance and uric acid levels in the context of thyroid health. The joint elevation of METS-IR and UA reveals a subgroup of individuals with significantly increased odds of prevalent thyroid nodules. Notably, while these elements were found to be interrelated, interaction analyses disproved a synergistic effect, suggesting that the relationship between these metabolic indicators and thyroid nodules may be more intricate than previously understood. Additionally, the exploration of SBP enhances understanding of the potential pathways linking metabolic dysfunction to thyroid pathologies.
The study successfully demonstrates that higher levels of both METS-IR and UA are linked to increased odds of prevalent thyroid nodules. This association shows a degree of nonlinearity across various C-TIRADS categories, suggesting the need for closer examination of metabolic indicators in individuals with thyroid conditions. Further longitudinal studies are warranted to establish causal relations and elucidate the underlying mechanisms affecting thyroid nodule prevalence in relation to metabolic health.