once a women reachs the age of 30 they lose 1% of their bone mass every year thereafter ,by the time a women is 50 she will have lost 20%
After age 30, for both men and women, bone mass undergoes a very slow, steady decline. Both estrogen and testosterone are important for maintaining bone mass. In women, bone mass takes a big drop in the years surrounding menopause, but then it levels off to a more gradual decline. Men have a slow decline throughout life; they don’t have the big drop that women have at menopause, but they can get osteoporosis, too, particularly if they smoke, drink large amounts of alcohol, or have a low testosterone level.