Association between serum cobalt concentration and thyroid function in pregnant women: A cross-sectional study

Maintaining normal thyroid function during pregnancy is crucial for maternal health as well as fetal growth and development. Exposure to environmental trace elements may influence thyroid function in pregnant women, but the specific role of cobalt remains unclear. This study aimed to systematically assess the relationship between serum cobalt concentration and thyroid function in pregnant women. Additionally, it explored cobalt's role within trace element mixtures to further elucidate its potential effects on thyroid function and provide theoretical and experimental foundations for future research.

This cross-sectional study included 293 pregnant women with valid trace element and thyroid function data from an initial 303 recruits. Measurements included serum cobalt, other trace elements (chromium, manganese, aluminum, vanadium, nickel), and thyroid indicators (Tg, TSH, FT3, FT4, TPOAb, TgAb).The relationships between serum cobalt and thyroid function, including potential non-linear effects, were analyzed using multiple linear regression, Bayesian kernel machine regression (BKMR), and restricted cubic spline (RCS) models. Additionally, interactions between cobalt and other trace elements were examined.

Higher cobalt exposure was significantly negatively correlated with FT3 and FT4 levels. The linear trend test (P for trend < 0.001) further supported this exposure-response relationship. BKMR analysis indicated that cobalt had the most significant effect on thyroid function among all the trace metals studied, with no significant interactions observed between trace elements. RCS analysis further revealed a non-linear correlation between cobalt and FT4, as well as a linear negative correlation with FT3. Spearman correlation analysis showed a positive correlation between cobalt and chromium, manganese, aluminum, and vanadium.

Elevated serum cobalt concentration was significantly associated with lower FT3 and FT4 levels in pregnant women. The findings suggest that cobalt may affect FT3 and FT4 through different mechanisms, with FT4 exhibiting a non-linear response, while FT3 declines in a stable linear manner. Cobalt was positively correlated with several trace elements; however, no significant interactions were observed among them. This suggests that cobalt's effect on thyroid function in pregnant women may be independent.