Both conditions hypogonadism and immobilisation (paraplegia) may contribute or lead to decreased bone mineral density resp osteoporosis. In this study bone mineral density is assessed in hypogonadal paraplegic patients, who are on standard prophylactic therapy for osteoporosis and and on a standard physiotherapy exercise program one group receiving Nebido for testosterone replacement (TRT). The additional effect of TRT on bone mineral density / osteoporosis is assessed (CT scan lumbar spine).