The role of triiodothyronine (T3) and T3/free thyroxine (fT4) in glucose metabolism during pregnancy: the Ma’anshan birth cohort study

Objectives: Compared with other thyroid markers, fewer studies have explored the associations between triiodothyronine (T3), T3/free thyroxine (fT4) and glucose abnormality during pregnancy. Thus, we aimed to: (i) examine the associations of T3 and T3/fT4 with glucose metabolism indicators and (ii) evaluate, in the first trimester, the performance of the two markers as predictors of gestational diabetes mellitus (GDM) risk. Methods: Longitudinal data from 2723 individuals, consisting of three repeated measurements of T3 and fT4, from the Man’anshan birth cohort study (MABC), China, were analyzed using a time-specific generalized estimating equat ion (GEE). The receiver operating characteristic curve (ROC) – area under the curve (AUC) and Hosmer– Lemeshow goodness of fit test was used to assess the discriminat ion and calibration of prediction models. Results: T3 and T3/fT4 presented stable associations with the level of fasting glucose, glucose at 1h/2 h during pregnancy. T3 and T3/fT4 in both the fi rst and second trimesters were positively associated with the risk of GDM, with the larger magnitude of association observed in the second trimester (odds ratio (OR) = 2.50, 95% CI = 1.95, 3.21 for T3; OR = 1.09, 95% CI = 1.07, 1.12 for T3/fT4). T3 ((AUC) = 0.726, 95% CI = 0.698, 0.754) and T3/fT4 (AUC = 0.724, 95% CI = 0.696, 0.753) in the first trimester could improve the performance of the prediction model; however, the overall performance is not good. Conclusion: Significant and stable associations of T3, T3/fT4 and glucose me tabolism indicators were documented. Both T3 and T3/fT4 improve the performance of the GDM predictive model.

Abstract licence: CC BY-NC

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