Eleven metabolites were found to have a causal association with an increased risk of osteoarthritis, including isovaleryl carnitine, taurocholate, kynurenine, acetaminophen 4-sulfate, homocysteine, serum iron, transferrin saturation, insulin-like growth factor-1, serum copper, and serum zinc. The gene discussed is IGF1; the disease is osteoarthritis.