Shanghai cohort of 91,941 pregnancies: thyroid and liver abnormalities in first trimester linked to hypertensive disorders

A retrospective cohort study of 91,941 pregnant women in Shanghai, covering 2014 to 2020, examined how first-trimester thyroid function relates to liver enzyme abnormalities and to later pregnancy complications. The results were published in the European journal of medical research biomedcentral.comEuropean journal of medical researchbiomedcentral.comOpen source ↗. Earlier work had linked abnormal liver biochemistry in early pregnancy to adverse outcomes, but its determinants and the role of the thyroid–hepatic axis remained incompletely understood.

The authors used multivariable logistic regression and restricted cubic spline models. Subgroup analyses were stratified by prepregnancy body mass index (BMI) and hepatitis virus infection status. This is an observational study, so it describes associations, not causation.

Thyroid hormones and liver enzymes

First-trimester free thyroxine (FT4) and thyroid-stimulating hormone (TSH) showed U-shaped associations with liver enzyme abnormalities (P-nonlinearity < 0.001). Compared with the reference group, women with FT4 above the 97.5th percentile had higher odds of liver enzyme abnormalities (adjusted odds ratio, aOR, 1.89; 95% CI 1.59–2.24). The same was true for TSH below the 2.5th percentile (aOR 2.47; 95% CI 2.13–2.87).

The estimates differed between subgroups. High FT4 was associated with higher odds of liver enzyme abnormalities in women who were underweight before pregnancy (aOR 2.86; 95% CI 1.90–4.28) and in women positive for hepatitis virus (aOR 2.27; 95% CI 1.02–5.07) biomedcentral.comEuropean journal of medical researchbiomedcentral.comOpen source ↗.

Combined abnormalities and complications

The highest risks were found when high TSH occurred together with alanine aminotransferase (ALT) above twice the upper limit of normal. For hypertensive disorders of pregnancy the aOR was 4.54 (95% CI 1.77–11.63). For intrahepatic cholestasis of pregnancy it was 6.09 (95% CI 1.44–25.87). The wide confidence intervals reflect the small number of women with this combined profile.

The authors conclude that early-pregnancy thyroid function is nonlinearly associated with liver enzyme abnormalities, and that prepregnancy BMI and hepatitis virus status should be taken into account. They state that integrated assessment of thyroid and liver biochemistry in early pregnancy may help identify women who warrant closer clinical evaluation.