A theoretical analysis of the changes in basic multicellular unit activity at menopause.

Bone loss at menopause is an important contributor to the development of osteoporosis in women. Although alterations in bone remodeling are the implied process through which bone is lost at menopause, how menopause influences basic multicellular units (BMUs), the teams of cells that perform bone remodeling, is not completely clear. In this analysis we utilize a computer simulation of BMU activity to evaluate the changes that occur at menopause. Transient and maintained changes in both the rate of bone turnover (expressed as the BMU birthrate or origination frequency) and the focal bone balance (differences between the amount of bone formed and resorbed at each remodeling site) are considered. The magnitude of the change in BMU activity is determined parametrically through comparison to lumbar spine bone mineral density data present in the literature. We find that a change in bone turnover that is maintained after menopause, a transient change in focal bone balance at menopause, or a combination of the two is consistent with bone loss patterns seen clinically. Understanding the changes in BMU activity that occur at menopause could lead to improved strategies to treat and prevent postmenopausal osteoporosis.