GCG and cerebrotendinous xanthomatosis: Here, we provide the first in-depth characterization of postprandial bile acid profiles, FGF19 and GLP-1 levels as well as glucose metabolism in the CYP27A1-deficient condition CTX and show profound alterations in postprandial bile acid profiles (absent elevations in CA and DCA species) and a blunted postprandial FGF19 response but intact postprandial GLP-1 responses in CTX patients as compared to healthy matched controls.