SERUM PARATHYROID-HORMONE AND CALCITONIN LEVELS FOLLOWING OVARIECTOMY IN THE ADULT-RAT

The ovariectomized rat is a reasonably good and often utilized model of human post-menopausal osteoporosis (Devlin and Ferguson, 1989). Mature rats were either ovariectomized or underwent a sham operation, killed at intervals following operation and the serum concentration of parathyroid hormone and calcitonin at death related to the histomorphometry of the cancellous bone of the proximal ilium. The mean serum calcitonin concentration for all ovariectomized rats was 66.4 pg/ml (SD = 18) and for the control rats was 76.42 pg/ml (SD = 20). The serum calcitonin concentration in the ovariectomized rats was significantly negatively correlated with the extent of erosion cavities of the cancellous bone (r = -0.598, t = -2.36, p = 0.039). No significant correlation was observed for the control rats (r = -0.107, t = -0.357, p = 0.727). The mean extent of erosion cavities in the ovariectomized group was 6.81 % (SD = 1.94) and in the control group was 6.47 % (SD = 2.2 1), with no significant differences between the two groups (t = 0.41, p = 0.69). No significant correlations were observed in serum parathyroid hormone (PTH) concentration with the bone resorption parameters. From this study it was concluded that calcitonin may be of aetiological importance in bone loss in the ovariectomized rat.