FT4

This study explored the relationship between early pregnancy thyroid markers and gestational diabetes mellitus (GDM) risk, along with the potential mediating role of lipid species. In a cohort of 6068 pregnant women, higher serum free thyroxine (fT4) levels were associated with a reduced risk of GDM (OR = 0.73, 95% CI 0.54–0.98), while an increased fT3/fT4 ratio was associated with a higher GDM risk (OR = 1.43, 95% CI 1.06–1.93). Lipidomic analysis identified specific lipids, including alkylphosphatidylcholine 36:1 and phosphatidylethanolamine plasmalogen 38:6, that were positively associated with the fT3/fT4 ratio. Mediation analysis suggested that 67.9% of the fT3/fT4 ratio’s effect on GDM risk was mediated by these lipid species. These findings highlight a link between thyroid function, lipid metabolism, and GDM development, with lipid species playing a significant mediating role.