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 less than 0.001), serum alkaline phosphatase activity (P less than 0.001), serum phosphate (P less than 0.001) and lower serum albumin (P less than 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.