Testosterone can boost bone density

Estrogen can protect bone density, but many doctors are reluctant to prescribe it for more than a short period of time because of studies such as the Women's Health Initiative, that used synthetic  estrogen (premarin). Bio-identical forms of estrogen have not been as extensively tested, but seem not to have the same side effects as the synthetic versions.  

Other hormones in addition to estrogen may also help build or maintain bone, including progesterone and testosterone. Here's a study that shows that testosterone and estrogen together boosted bone density more than estrogen alone. Also, low testosterone in men is associated with risk of osteoporosis. Another study showed that progesterone complements estrogen in preserving bone and deserves to be studied more for that benefit. A helpful side effect of oral progesterone is that it promotes deep sleep. 

There are doctors who will work with you to test hormone levels and find a combination of bio-identical hormones to help your body build and maintain bone. All 3 sex hormones seem to be important to healthy bones, so it's worth investigating with your doctor.