An implantable tissue growth stimulator is disclosed. The implantable tissue growth stimulator includes electronic circuitry to alter the voltage output by the stimulator. The implantable tissue growth stimulator may he controlled from an external device via wireless communication. The implantable tissue growth stimulator may be configured for use with an implants in particular, the implantable tissue growth stimulator may be incorporated into an orthopedic device such as a hip prosthesis. The implantable tissue growth stimulator may be used to stimulate bone growth.