In the CRC group, the serum levels of free primary bile acids including CA, CDCA, as well as secondary bile acids such as DCA, GDCA, TDCA, LCA, GLCA, TLCA, UDCA, GUDCA, TUDCA, were significantly lower than those in the HC group (P < 0.05). The gene discussed is GNAT3; the disease is colorectal carcinoma.