Hypo-, hyperthyroidism causally linked to pre-eclampsia

Hyper- and hypothyroidism are causally associated with pre-eclampsia (PE), but PE does not causally influence thyroid dysfunctions, suggest the results of a Mendelian randomization (MR) study. 

“Thyroid dysfunction has been associated with PE during pregnancy, but the observational results are conflicting,” the investigators said. “Our study aims to investigate the causal association and direction between genetically predicted effects of thyroid function on PE and vice versa via two large summary genetic data.” 

This two-sample bidirectional MR study used genome-wide association studies (GWAS) summary data from two European cohorts, namely the TyroidOmics Consortium and the FinnGen Biobank. 

The investigators used random effects inverse variance weighted (IVW) for the main analysis and MR-Egger and weighted median for the sensitivity analysis. They also performed a statistical analysis using the R program with the two-sample package. 

Genetically predicted hyperthyroidism (β, 0.06, 95 percent confidence interval [CI], 1.01–1.12; p=0.02) and hypothyroidism (β, 0.11, 95 percent CI, 1.03–1.21; p=0.01) were causally associated with PE during pregnancy. These associations persisted in sensitivity analysis. 

On the other hand, PE showed no causal association with the risk of thyroid dysfunction in the reverse MR results: thyroid-stimulating hormone (β, 0.00; p=0.92), free thyroxine (FT4; β, –0.01; p=0.56), triiodothyronine (FT3; β, –0.00; p=0.72), FT3/FT4 (β, –0.01; p=0.38), thyroid peroxidase antibodies (β–0.01; p=0.64), hyperthyroidism (β, –0.11; p=0.29), and hypothyroidism (β, 0.04; p=0.12).