Method and composition for reducing or preventing bone resorption

An anti-osteoclastic composition containing a proteoglycan 4 in a pharmaceutically acceptable carrier is administered to a human or animal suffering from a pathological bone condition such as osteoporosis in a sufficient amount to reduce, delay onset of or prevent excessive bone resorption in which the rate of bone resorption exceed the rate of bone formation. Excessive bone resorption is inhibited by preventing the formation or activity of osteoclasts. Osteoporosis is linked to bone fracture, a debilitation condition often resulting in the need for risky, invasive surgery, and the possible consequence of permanent immobilization, especially in elderly populations.