THE DECREASE IN BONE MASS ASSOCIATED WITH AGING AND MENOPAUSE

The human skeleton accumulates bone up to approximately age 30, after which bone is gradually lost. Although estrogen replacement therapy pr events postmenopausal bone loss, it is not certain that estrogen defic iency alone is responsible for the decrease in bone mass. Progesterone deficiency could also be a factor, and progesterone replacement thera py has been shown to prevent postmenopausal bone loss associated with ovarian dysfunction. This article reviews what is known about bone rem odeling and bone loss as a function of age and gender, discusses evide nce from studies in rats that progesterone plays an important role in regulating bone formation, and suggests direct ions for future studies in predicting the success or failure of implant therapy based on the number and kinds of osteoprogenitor cells present.