Provided herein are methods of using 7a-hydroxy-4-cholsten-3-one (C4) in predicting the clinical sensitivity to treatment of bile acid-related and associated disorders with treatment peptides, such as variants of fibroblast growth factor 19 (FGF19) proteins and peptide sequences (and peptidomimetics) and fusions of FGF19 and/or fibroblast growth factor 21 (FGF21) proteins and peptide sequences (and peptidomimetics), and variants of fusions of FGF19 and/or FGF21 proteins and peptide sequences (and peptidomimetics).
