At menopause, there's a big drop in levels of the hormone estrogen, making the body lose bone faster. Eventually, the rate of bone loss goes back to what it was before menopause. But the pace of making new bone doesn’t. That cuts bone mass and gives postmenopausal women a much greater chance of having a fracture.
Early menopause (before age 40) also raises the chance of osteoporosis and fractures. So do long periods of time when hormone levels are low or absent.