Hypothyroidism and related diseases: a methodological quality assessment of meta-analysis

There is an increasing prevalence of hypothyroidism and there is a growing body of meta-analyses (MAs) on the association between hypothyroidism and other diseases. However, the methodological quality of the MAs significantly varies. Thus, this study aimed to evaluate and summarise data on the methodological quality of MAs on the associations between hypothyroidism and other diseases using the Assessment of Multiple Systematic Reviews (AMSTAR) scale, providing suggestions for clinical decision-making processes.

To assess the methodological quality of MAs using the AMSTAR scale.

A systematic literature search was performed in PubMed, EMBASE, the Cochrane Library, web of science and Chinese Biomedicine Literature Database.

We included MAs that had assessed the association between hypothyroidism and other diseases in humans and that had full texts regardless of the publication status. No restriction applied on language or date.

Two reviewers independently screened the titles and abstracts of all searched literature to acquire potentially eligible publications. The full texts of possible eligible publications were downloaded and assessed. Inconsistent comments were resolved through discussions with a third reviewer.

52 studies were included. The average AMSTAR score of the included articles was 8.6 (range: 5-10), and those of English and Chinese MAs were 8.8 and 7.0, respectively. A total of 52 MAs were evaluated, and 19 (36.5%) and 33 (63.5%) of these MAs were of moderate and high quality, respectively. None of the MAs were of low quality. Only two MAs had an a priori design. Items 3, 5 and 9 had the highest compliance (50/52, 96.2%), and aside from item 1, items 7 and 8 had the lowest compliance (33/52,63.5%). According to the results of these MAs, hypothyroidism was significantly associated with cardiovascular diseases, metabolic diseases, neuropsychiatric disorders, breast cancer and pregnancy outcome.

The methodological quality of the included MAs on the association between hypothyroidism and other diseases was moderate to high. MAs with high qualities confirmed that hypothyroidism was significantly associated with cardiovascular diseases, metabolic syndrome, preterm birth and neonatal outcomes. Consideration of scientific quality when formulating conclusions should be made explicit and more attention should be paid to improving the methodological quality of MAs, and increasing their applicability for clinical decision-making.