Effect of ovariectomy on cancellous bone in the hypophysectomized rat

This experiment studied the effects of hypophysectomy (HX) and ovariectomy (OV) on cancellous bone in the proximal tibia and distal 5th lumbar vertebra by dynamic histomorphometry. Forty-eight female Sprague-Dawley rats, 3 months of age, were divided into age-matched control, HX, OV, and HX + OV (HO) groups. Ten rats were sacrificed at 3 months of age as baseline controls, and the rest of the animals were sacrificed 5 weeks after the surgery. While the age-matched controls, and the OV rats significantly increased in body weight compared with the baseline control rats, cancellous bone volumes in the proximal tibia and distal 5th lumbar vertebra increased in the age-matched controls and decreased in the OV rats. In the HX and HO rats, body weight equaled baseline control values, and their cancellous bone volumes were decreased with a poorer trabecular architecture in both bone sites. In all HX, OV, and HO rats, uterine weight and serum estradiol were significantly decreased. OV significantly increased longitudinal bone growth and the tissue- and surface-based bone formation and bone resorption parameters in both the proximal tibia and 5th lumbar vertebra (p < 0.05). HX alone or HO significantly decreased longitudinal bone growth and the tissue-based bone formation rate without significantly affecting surface-based bone formation and bone resorption parameters when compared with the age-matched controls. No significant differences were detected in any variables between the HX alone and HO rats.(ABSTRACT TRUNCATED AT 250 WORDS)