GDF2 and metabolic syndrome: When BMP-9 levels were in the tertile 2 and tertile 3, the odds ratios of developing MetS were 0.461 (95% CI 0.259; 0.819) and 0.145 (95% CI 0.081; 0.258), respectively (vs. tertile 1, both P < 0.01; Fig. 1C).