In another case-controlled study conducted in the US, a higher concentration of free triiodothyronine (FT3), the biologically active thyroid hormone, or a higher FT3/FT4 ratio (top quartile vs. bottom quartile) was associated with a 3.89–13.6-fold increase in the GDM risk, whereas no significant independent association was found between the FT4 concentration and GDM risk [16]. The gene discussed is TG; the disease is gestational diabetes.