The effects of continuous progestogen treatment on cortical bone remodeling activity in beagles.

Cortical bone remodeling measurements were carried out on the ribs of 6 spayed and 5 progestogen-treated spayed Beagle dams which had been subjected to a period of observation equal to more than 1 sigma of intact canine bone remodeling activity. Analyses of static and dynamic features indicated that continuous medroxyprogesterone acetate replacement therapy altered the rates of cortical bone remodeling activity. In the progestogen-treated dams, more Basic Multicellular Units (BMUs) were activated, exhibiting shortened resorption and formation times. Thus, this progestogen appears to play a significant role in regulating cortical bone cell activity and, as such, suggests that progesterone may play a part in the prevention or slowing down of cortical bone loss in females following menopause or oophorectomy.