Effects of oophorectomy on biochemical and bone variables in the rat

The metabolic effects of oophorectomy (Oophx) were studied in 6-month-old rats maintained on a normal chow diet. Nine weeks following operation, Oophx animals had a significantly lower femoral trabecular bone volume (BV/TV) than sham-operated animals; mean (SD) Oophx 8.5 (3.8)%; Sham 13.4 (2.5)%; P = 0.013). They also had a higher urine hydroxyproline ( P < 0.001), serum alkaline phosphatase activity ( P < 0.001), serum phosphate ( P < 0.001) and lower serum albumin ( P < 0.001) than the controls. Serum osteocalcin was inversely related to the BV/TV in the Oophx animals at 9 weeks post operation ( r = −0.85, P = 0.007, n = 8). A fall in serum ionized calcium from 3 to 9 weeks post operation correlated with a fall in urinary hydroxyproline in the Oophx animals ( r = 0.57, P = 0.002, n = 27). The data are consistent with a model of ovarian hormones acting directly to modulate bone cell activity as well as exerting an effect on the renal handling of phosphate.