A systematic review and meta-analysis investigating the relationship between metabolic syndrome and the incidence of thyroid diseases

Abstract

Purpose To assess the prospective association between metabolic syndrome (MetS), its components, and incidence of thyroid disorders by conducting a systematic review and meta-analysis. Methods A systematic search was performed in Ovid Medline, Embase.com, and Cochrane CENTRAL from inception to February 22, 2023. Publications from prospective studies were included if they provided data on baseline MetS status or one of its components and assessed the incidence of thyroid disorders over time. A random effects meta-analysis was conducted to calculate the odds ratio (OR) for developing thyroid disorders. Results After full-text screening of 2927 articles, seven studies met our inclusion criteria. Two of these studies assessed MetS as an exposure (N = 71,727) and were included in our meta-analysis. The association between MetS at baseline and incidence of overt hypothyroidism at follow-up yielded an OR of 0.78 (95% confidence interval [CI]: 0.52–1.16 for two studies, I2 = 0%). Pooled analysis was not possible for subclinical hypothyroidism, due to large heterogeneity (I2 = 92.3%), nor for hyperthyroidism, as only one study assessed this association. We found evidence of an increased risk of overt (RR: 3.10 (1.56–4.64, I2 = 0%) and subclinical hypothyroidism (RR 1.50 (1.05–1.94), I2 = 0%) in individuals with obesity at baseline. There was a lower odds of developing overt hyperthyroidism in individuals with prediabetes at baseline (OR: 0.68 (0.47–0.98), I2 = 0%). Conclusions We were unable to draw firm conclusions regarding the association between MetS and the incidence of thyroid disorders due to the limited number of available studies and the presence of important heterogeneity in reporting results. However, we did find an association between obesity at baseline and incidence of overt and subclinical hypothyroidism.

Obesity and Obesity-Related Thyroid Dysfunction: Any Potential Role for the Very Low-Calorie Ketogenic Diet (VLCKD)?

“…On the other hand, another meta-analysis showed a high degree of heterogeneity among the studies, and it was not conclusive in the relation of both pathologies. However, an association was found between obesity and the incidence of overt and sHypo [ 71 ].…”

Subclinical Hypothyroidism in Patients with Obesity and Metabolic Syndrome: A Narrative Review

“…Thyroid hormone (TH) controls food intake by regulating appetite and thermogenesis and influences glucose and lipid metabolism and adipogenesis [ 5 ]. MetS, obesity and SHypo are frequent conditions among the adult population and to date, various studies and meta-analyses have been published to assess the relationship between these disorders with controversial results [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. Some meta-analyses assessed the relationship between SHypo and MetS, as well as its components.…”

“…The TSH threshold value for the diagnosis of SHypo and the confounding factor correction had no effect on the relationship between MetS and SHypo [ 9 ]. Another recent meta-analysis, however, which included data from prospective studies assessing the association between metabolic syndrome (MetS) and incidence of SHypo, showed different findings [ 10 ]. Due to the high degree of heterogeneity among the limited studies that are available, there is no conclusive evidence regarding the relationship between the occurrence of overt or subclinical hypothyroidism in individuals with MetS [ 10 ].…”

“…Another recent meta-analysis, however, which included data from prospective studies assessing the association between metabolic syndrome (MetS) and incidence of SHypo, showed different findings [ 10 ]. Due to the high degree of heterogeneity among the limited studies that are available, there is no conclusive evidence regarding the relationship between the occurrence of overt or subclinical hypothyroidism in individuals with MetS [ 10 ]. The Health, Ageing and Body Composition study reported evidence of an association between SHypo prevalence, but not incidence of MetS [ 11 ].…”