The present invention relates to a composition useful for the diagnosis of diseases associated with aberrant expression of the genes encoding the secreted proteins Futrin 1, 2, 3 and/or 4(=R-Spondin 2, 3, 1 and 4, respectively), e.g. in connection with tumors or diseases of the muscle, kidneys or bones. The present invention also relates to a pharmaceutical composition containing a compound which is capable of modifying (a) the expression of the gene encoding Futrin 1, 2, 3 and/or 4 or (b) the activity of the Futrin 1, 2, 3 and/or 4 protein.