A cross-sectional study on the associations between serum metal exposure and thyroid hormones in chinese pregnant women

Prenatal exposure to environmental metals has been increasingly recognized as a crucial factor influencing maternal thyroid function, which plays a vital role in regulating metabolism, maintaining pregnancy, and supporting fetal neurodevelopment. However, the effects of emerging or less-studied metals, such as titanium (Ti), selenium (Se), and strontium (Sr), on thyroid hormone homeostasis during pregnancy remain poorly understood. In this cohort of 495 pregnant women, 12 of 19 metals showed detection frequencies above 90%. After adjusting for major confounders, Ti exposure was negatively associated with Total triiodothyronine (FT4), while Se and Sr showed consistent inverse associations with Total triiodothyronine (TT3) and Free triiodothyronine (FT3), indicating potential disruption of thyroid hormone synthesis and conversion. Mixture analyses using WQS and BKMR further identified key metals contributing to altered thyroid hormone levels and suggested heterogeneous directions of association within the metal mixture. These findings reveal previously unrecognized associations between Ti, Se, Sr, and maternal thyroid hormone alterations, providing new insights into the endocrine effects of environmental metal exposure. This study expands the understanding of how both essential and non-essential metals influence maternal thyroid function, emphasizing the need for stricter environmental monitoring and preventive strategies to protect maternal endocrine health and optimize fetal developmental outcomes.