GDF5 and Osteopenia: However, in own studies in a senile sheep defect model of lumbar osteopenia, matched doses of GDF-5 (1, 5, 100, and 500 μg) proved at least as effective as the respective BMP-2 doses, showing that, possibly depending on the location, GDF-5 or its mutant BB-1 can be as potently osteoinductive as BMP-2 [24–26].