As most people age bone mass is lost to varying degrees. This is especially true in Caucasian post- menopausal women. When a woman has her monthly menstrual period, hormones are secreted that help maintain bone health. After menopause these hormones are no longer being secreted into the bloodstream. Combined with other factors like deficiencies of calcium, phosphorus, and vitamin D, the bones of these women become brittle and porous. The bones lose mass and strength due to the loss of intracellular and extracellular bone matrix. These women are susceptible to spontaneous fractures.
Another reason most people lose bone mass as they age is related to activity levels. Most (not all) people have a decrease in physical activity levels as they age. Physical activity helps to strengthen bones and maintain the overall health of bone tissue.