Women generally have lighter, thinner skeletal frames than men and thus have less bone reserve of calcium. Women also lose bone rapidly after menopause. Men lose calcium from bone, but not at the high rates seen in women. African and Hispanic Americans have a lower, but still significant, incidence of osteoporosis. Those who have had a parent with osteoporosis are at a greater risk for developing the disease themselves.
Smaller bones provide smaller reserves of calcium to the body.
In women, the sex hormone estrogen protects against bone loss. After menopause, women lose the ability to produce estrogen. This is one of the reasons women may opt for hormone replacement therapy after menopause. Women who go into menopause early, either from an illness or surgery, are of special concern because they lose the bone protection from estrogen that much earlier. In men, the sex hormones testosterone and estrogen protects against bone loss.