Is hyperemesis gravidarum associated with transient hyperthyroidism? A systematic review and meta-analysis

Emerging evidence suggests an association of hyperemesis gravidarum (HG) with transient hyperthyroidism and high HCG levels. For synthesizing the current evidence to determine the association between HG with hormones related to thyroid function, a comprehensive systematic search was performed in the electronic databases comprised Medline, Web of Science, Scopus, Embase, ProQuest, and Cochrane Library up to December 2021. All published observational studies that evaluated the association of hyperemesis gravidarum with transient hyperthyroidism were investigated considering the PICO method. The standardized Joanna Briggs Institute Meta-Analysis of Statistics, Assessment, and Review Instrument were applied to appraise the included studies. Twenty-nine studies consisted of 6525 women included in the systematic review. Among them, 28 studies with 2446 participants were included in the meta-analysis. There were significant associations of HG with fT3 (MD: 1.31 pg/mL, 95% CI: 0.61 to 2.01), fT4 (MD: 1.95 ng/dL, 95% CI: 1.17 to 2.73), TSH (MD: -1.22μIU/mL, 95% CI: -1.75 to -0.68), TT4 (MD: 0.56 nmol/L, 95% CI:-0.43 to 1.24), and HCG (MD: 1.90IU/L, 95% CI: 0.497 to 3.301). In conclusion, the serum levels of fT3, fT4, and TT4 increased but TSH decreased significantly in women with compared without HG, indicating the significant association of HG with GTT.