Abstract

Osteoporosis is a global problem which results in increased fractures risk. The reports from earlier studies were inconsistent with the aging factor as well as the time which is needed to induce bone loss post-ovariectomy. This study aimed to determine the short-term effects of estrogen deficiency on bone structural histomorphometric parameters in young rats. 30 Sprague-Dawley female ratsweighing 250 to 300 g were assigned to baseline, sham-operated and ovariectomy groups. The baseline group (n = 10) was sacrificed immediately. Sham-operated rats (SO, n = 10) underwent sham operation while ovariectomised group (OVX, n =10) underwent bilateral ovariectomy. All the rats were sacrificed 6 weeks post-ovariectomy. Following sacrifice, the right femora were dissected and subjected to the histomorphometric analysis using modified Von Kossa method. Bone volume/tissue volume (BV/TV) and trabecular number (Tb.N) reduced significantly, while trabecular separation (Tb.Sp) increased significantly in the ovariectomized rats, compared to the baseline and sham groups 6 weeks post-ovariectomy (P<0.001). In the other hand, trabecular thickness (Tb.Th) was consistent among the groups (P=0.41).  Estrogen deficiency resulted in marked decline in BV/TV which most probably attributed to a reduction in Tb.N. In contrast, Tb.Th was found to be preserved following estrogen loss. Hence, the period of 6 weeks post-ovariectomy was sufficient to induce osteoporosis in ovariectomized rats without affecting Tb.Th.

Key words: Bone histomorphometry, menopause, estrogen deficiency, osteoporosis, ovariectomy, trabecular bone.