The ovariectomized sheep as a model for human bone loss.

The aim of this study was to determine the effects of ovariectomy on the trabeculae of ovine iliac bone, with a view to the further development of a model for human osteoporosis. Seven ovariectomized (OVX) and five control Dorset ewes were observed for one year. Iliac crest bone samples were obtained at the time of ovariectomy ("time 0") and again when the animals were killed 12 months later. At "time 0" and at 3-month intervals thereafter samples of blood and urine were collected for the assay of serum 17beta-oestradiol and osteocalcin (OC) and urinary deoxypyridinium (D-PYR). One year after ovariectomy, trabecular bone volume and thickness were reduced (P<0.05) and trabecular separation was increased (P<0.05) as compared with the controls. In OVX sheep, serum 17beta-oestradiol concentrations were significantly lower at the end of the experiment than at "time 0", while serum OC and urinary D-PYR concentrations were significantly higher (P<0.001). The results suggest that the OVX sheep is a valid model for changes in trabecular bone architecture associated with oestrogen deficiency, especially in women experiencing early menopause.