About 99 percent of the body's calcium is stored in bones and teeth. Bone is continually being broken down and rebuilt. If the amount of calcium absorbed equals the amount lost, a state of balance occurs. But when dietary intake of calcium can't meet the body's needs, the body draws the mineral from bones to allow a constant bloodstream supply. Ultimately, the breakdown process can exceed deposits, causing a possible reduction in bone mass and density.
Osteoporosis is seen less often in men than in women for several reasons.
Men generally have greater bone mass than women, and in males, bone loss begins later and advances more slowly. But men do have a hormonal drop-off in testosterone similar to women's reduction of estrogen after menopause. Testosterone may diminish as a result of hypogonadism, a condition marked by decreased function of the testicles. Testosterone levels may naturally become lower as a man ages. Whether that translates to osteoporosis depends on how much bone you have when the loss begins and how quickly you lose it.