Treating a disorder (e.g., osteoporosis, renal failure, or diabetic nephropathy) associated with a signaling pathway mediated by IL-20 receptor with an agent that suppresses IL-20 receptor activity, e.g., an antibody that neutralizes IL-20 receptor via binding to IL-20R1, an antisense nucleic acid that suppresses expression of IL-20R1, a small molecule that inhibits IL-20 receptor activity, or a dominant negative mutant of IL-19, IL-20, or IL-24.