I had a hysterectomy at 46 yrs old and had my first bone density scan at 56. It showed that I had osteopenia at that time. My doctor told me to take 1200 mg/day of calcium in an effort to stop the loss; however, I actually ended up rebuilding some that I'd lost, which I thought was pretty cool.
Vitamin D is necessary for proper absorption of calcium, as is magnesium. Many of us are low in Vitamin D, especially, those that live in areas that have longer/colder winters and can't get outside for adequate sun. Many of us are deficient in D for other reasons as well. Vitamin K is also necessary to make sure calcium gets to the bones (Vitamin K can affect blood clotting).
My doctor says that most women should take around 1000 - 1200 mg/day of calcium, but it should be taken in divided doses because the body can only absorb up to 600 mg at one time.
Excess calcium (hypercalcemia) in the blood can also contribute to kidney stones as well as affect the heart, but typically, only if taking more than 1500 mg/day. Hypercalcemia in the blood is typically caused by parathyroid malfunction. Calcium controls electrical impulses in the body.
Along with calcium, magnesium and Vitamin D, exercise is also necessary to prevent bone loss and/or to help rebuild it.
We're all different, so it's always best to consult your doctor about supplements. I have to balance my calcium intake between taking enough to try to help prevent bone loss, but not so much that it makes my kidney stones worse.
Calcium should not be taken within 4 hours of many medications, especially, replacement thyroid hormones, as calcium inhibits absorption of the medication. Since I have Hashimoto's/hypothyroidism, I take thyroid med in the AM, 500 calcium at noon and 500 at bedtime.
One other thing - I am on the fence regarding calcium supplements because you don't want to take too much calcium since it's bad for the heart. I take one that has calcium, magnesium and phosphorus in a 2:1:1 ratio. But I do not take it consistently because I'm not sure I should take it! Your thoughts??
Many women do lose bone after menopause, supposedly due to the loss of estrogen. But I suspect that loss of progesterone also plays into it. Testosterone is critical to bone health too. However, although testosterone levels drop around menopause, they gradually increase to reach reproductive levels in a woman's 70's if she is intact. Hysterectomized women have lower levels of testosterone and women whose ovaries were removed have even lower levels (along with other hormone deficiencies).
Of course, besides organ removal, there are women that are more at risk than others such as those who are thin or of slight build. And there are other factors such as history of steriod use, thyroid disease that is not "properly" managed or other endocrine abnormalities (premature ovarian failure, adrenal dysfunction). For instance, one of my sisters has especially bad osteoporosis because she has Hashimoto's thyroid disease which has made her thyroid hormone levels difficult to manage plus she has had to take steroids (e.g. Prednisone) a number of times and she has a somewhat slight build.