In order to investigate the histological and immunohistochemical changes of thyroid glands, and serum osteocalcini estradiol, pmgesterone, follicular-stimulating hormone (FSH), and calcium levels in the osteoporotic rats induced by ovariectomy, normal(sham-operated group) and experimental groups(ovariectomized group) were divided. The experimental groups were subdivide6 to 5, 10, 15, and 20 weeks after ovariectomized groups. The histological structure of the thyroid gland were observed in normal structure throughout all experimental periods but the calcitonin-immunoreartive cells in the experimental groups were significantly decreased compared with normal groups and degranulations of calcitonin-immunoreactive cells were observed. Theses numbers were decreased with time after ovariectomy. However, the serum osteocalcin and FSH levels of experimental groups were significantly increased compared with normal groups and these levels were increased along with time after ovariectomy, but serum estradiol, progestemn and calcium levels of experimental group were significantly decreased compared with normal groups and these levels were decreased with time after ovariectomy.