Osteoporosis has multiple causes. Cases of osteoporosis may be broadly divided into categories and types, based on major risk factors. Secondary osteoporosis is associated with some medical conditions and the use of some medications . Diet and lifestyle factors may also increase the risk of osteoporosis. The most important cause is the loss of reproductive hormones.
Bones are dynamic organs which store and release calcium continuously.
In childhood and early adulthood, bones store calcium faster than they release it, which contributes to growth. Around age 30, bones achieve peak mass. The rate of calcium storage slows to the rate of calcium release. Peak bone mass is usually retained throughout reproductive life. Thereafter, roughly in parallel with decreasing levels of reproductive hormones, bones release calcium faster than they store it, resulting in demineralization, weakening, and increased risk of fracture.