Up until approximately age 30, as calcium is added to the diet, the rate at which bone is replaced is greater than the rate at which it breaks down. By age 30, you've reached your peak bone mass - the point at which your bones are as dense and as strong as they'll ever be. By age 40, bone mass begins to slowly decline. After menopause, women lose bone mass rapidly due to a drop in estrogen level. For the next five to 10 years they lose about two to three percent of bone mass each year.
Mineral deposits leave the honeycomb structure faster than they can be replaced.
In other words, the rate at which bone breaks down becomes greater than the rate at which it can be replaced. Bones with less mass are more likely to break or fracture, even in a minor fall. The first warning that you have osteoporosis may be a broken bone. This has been the case with many postmenopausal women who have broken bones in their wrists or spines as a result of lowered estrogen levels. In other instances, fractures of the spine have resulted in both a loss of height and rounded shoulders, often referred to as a dowager's hump.