Many studies discussed the adverse effects of bilateral orchidectomy on the male reproductive tract and bone in patients with metastatic cancer prostate. The aim of the present work is to detect the effect of calcitonine on the lumbar vertebrae and prostate following orchideetomy. One hundred and ninety-eight adult male albino rats were divided into four groups; control, sham-operated, prchidectomized rats, and orchidectomized rats injected with calcitonine. The present work demonstrated that bilateral orchidectoniy produced osteoporotic changes in bone and atrophic changes in the prostate which were partially limited by the injection of calcitonine.