Emotion-Regulation Difficulties and Skills in the Cross-Sectional Association Between Thyroid Function and Antenatal Distress in Hypothyroid Pregnancy

Background/Objectives: Thyroid dysfunction and emotion-regulation difficulties are each linked to antenatal distress but are rarely measured in the same women. We examined whether emotion regulation accounts for the cross-sectional association between thyroid biochemistry and antenatal distress in hypothyroid pregnancy. Methods: In this single-center cross-sectional study, 360 pregnant women with hypothyroidism completed measures of emotion-regulation difficulties and skills and four distress measures at one antenatal visit, alongside thyroid testing. Exposures were standardized log thyroid-stimulating hormone (TSH) and free thyroxine (free T4); the outcome was a composite distress score. Parallel two-mediator models with covariate adjustment were fitted, and bias-corrected bootstrapping was used to estimate the indirect associations. Results: Higher log TSH (total association 0.189, 95% confidence interval [CI] 0.108 to 0.272) and lower free T4 (−0.200, 95% CI −0.278 to −0.120) were associated with greater distress. Most of each association was statistically accounted for by emotion-regulation difficulties and skills; direct associations included zero. Apparent route-specific moderation by gestational week and by thyroid autoimmunity was not supported, because the two indices did not differ. Conclusions: Measurement at a single visit leaves temporal ordering unidentified, so these findings decompose a cross-sectional association rather than demonstrate causal mediation; within that constraint they support assessing emotion regulation alongside thyroid monitoring and depression screening.