The major findings of the present study are 1) circulating BMP-9 levels are lower in subjects with MetS compared with healthy controls; 2) circulating concentrations of BMP-9 significantly decreased with more than 3 components of MetS; 3) plasma BMP-9 concentrations are significantly associated with MetS even after controlling for anthropometric variables, lipid profiles and hormone levels. This evidence concerns the gene GDF2 and metabolic syndrome.