Polypeptides of HFGAN72 receptor ligands and polynucleotides encoding the polypeptides are provided. Methods of using these polypeptides to diagnose diseases relating to the under- or over-expression of HFGAN72 receptor ligands are also provided. In addition, methods of identifying agonists or antagonists of the interaction of HFGAN72 receptor ligands with the HFGAN72 receptor are provided. Methods of treatment by administering the identified agonists or antagonists to patients in need thereof are further disclosed.