Association Between Metabolic Syndrome and Subclinical Hypothyroidism: A Systematic Review
Bibliographic record
Abstract
Metabolic syndrome (MetS) and subclinical hypothyroidism (SCH) are prevalent endocrine-metabolic disorders with significant cardiovascular implications. Emerging evidence suggests a bidirectional relationship between these conditions, but findings remain inconsistent across populations. This systematic review synthesizes existing literature to evaluate the association between SCH and MetS, focusing on prevalence, demographic variations, and mechanistic links. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a comprehensive search was conducted across PubMed, Scopus, Web of Science, and Embase up to April 2025. Twelve observational studies (cross-sectional, cohort, and case-control) were included after screening. Studies were selected based on predefined criteria: adult populations (≥18 years), clear definitions of SCH (elevated thyroid-stimulating hormone (TSH) with normal free thyroxine 4 (FT4)) and MetS (National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III), International Diabetes Federation (IDF), or Joint Interim criteria). Data were extracted on study characteristics, prevalence rates, and metabolic associations. Quality assessment used the Newcastle-Ottawa Scale. SCH prevalence was significantly higher in MetS patients (range 8.9-37%) as compared to controls, with notable geographic and gender disparities. Key findings included: (1) Strong associations between SCH and central obesity, dyslipidemia, and hypertension; (2) Gender-specific risks, with males showing higher MetS incidence and females exhibiting higher SCH prevalence; (3) Age-related trends, with SCH prevalence increasing with age, though no elevated risk was observed in individuals ≥50 years. Longitudinal data suggested MetS may predict SCH development. This review supports a significant association between SCH and MetS, driven by shared pathways involving lipid metabolism, insulin resistance, and adiposity. Demographic variations underscore the need for tailored screening, particularly in high-risk groups. Standardized diagnostic criteria and prospective studies are warranted to clarify causality and therapeutic implications.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.005 | 0.022 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.009 | 0.010 |
| Bibliometrics | 0.008 | 0.009 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".