Subclinical hypothyroidism and the risk of metabolic syndrome: A meta-analysis of observational studies

Abstract

Background: Observational studies on the association between subclinical hypothyroidism (SCH) and metabolic syndrome (MetS) have produced inconsistent results. Therefore, we performed a meta-analysis to evaluate the effect of SCH on the risk of MetS.

Methods: Multiple databases were searched to identify studies on the association between SCH and the risk of MetS, up to February 2015. Relevant information for analysis was extracted. A random-effects model was used to calculate the pooled risk estimates.

Results: 9 studies (7 cross-sectional and 2 case-control studies) were included. The pooled odds ratio (OR) for MetS comparing SCH with euthyroid subjects was 1.31 (95%CI: 1.08 to 1.60, p = 0.006, I(2) = 50%). Subgroup analyses by countries revealed a significant association for the studies from Asian (OR = 1.244, 95% CI: 1.030-1.503, I(2) = 25%) other than non-Asian (OR = 1.548, 95% CI: 0.925-2.591, I(2) = 73.5%) countries. A positive association was identified in the IDF subgroup (OR = 1.288, 95% CI: 1.055-1.572, I(2) = 0%), but not in the NCEP-ATP III (OR = 1.351, 95% CI: 0.950-1.923, I(2) = 66.4%), Chinese (OR = 1.430, 95% CI: 0.891-2.294) and Japanese (OR = 1.542, 95% CI: 0.594-4.005, I(2) = 78.3%) subgroup. A certain degree of heterogeneity was observed among studies which cannot be explained by study design, diagnostic criteria and location.

Conclusion: Our results demonstrated that SCH was significantly associated with a higher risk of MetS. Well-designed cohort studies were warranted to confirm our findings.

Keywords: Subclinical hypothyroidism; meta-analysis; metabolic syndrome.