Gender and Risk of Congenital Hypothyroidism: A Systematic Review and Meta-Analysis

Background: Although numerous observational studies have investigated the association between gender and risk of congenital hypothyroidism, the role of gender as a risk factor for congenital hypothyroidism remains unknown.Thismeta-analysis was conducted to summarize the epidemiologic evidence of the effect of gender on the congenital hypothyroidism occurrence, and also to identify the sex ratio for congenital hypothyroidism. Materials and Methods: A comprehensive literature search of numerous electronic databases including PubMed, Scopus, EMBASE, and Science Direct was performed until February 1st, 2017. All studies designed case-control (six studies with 3,254 subjects) and cross-sectional studies (eight studies with 8,258,745 subjects) addressing the association by odds ratio (OR) and 95 confidence interval (95 CI) were included. Moreover, eleven cross-sectional studies were also included providing a sex ratio for congenital hypothyroidism. Pooled Mantel-Haenszel OR (MH OR) with 95 CI was estimated using the random-effects method. Results The overall summary results showed that girl gender is associated with an increased risk of congenital hypothyroidism (pooled MH OR=1.46; 95CI: 1.10, 1.95). The pooled MH OR for case-control studies was 1.69 (95CI: 1.35, 2.13), whereas the pooled MH OR for cross-sectional studies was 1.26 (95CI: 1.00, 1.59). In addition, pooled female to male sex ratio of congenital hypothyroidism incidence was 1.35 (95CI: 0.99, 1.83). Conclusion: The results of this meta-analysis provide evidence for a higher risk in girl gender for developing congenital hypothyroidism. More epidemiological and clinical studies are needed to explore why girl gender is at increased risk of congenital hypothyroidism compared with boy.