You are at a good age to consider starting HRT, especially if you are within 10 years post-menopause. 0.05mg/day estradiol patch (or equivalent dose in other dosage form) is considered as the "standard" dose used for osteopenia and osteoporosis. However, some studies suggest that a lower dose - 0.025mg/day patch - can also be effective. A few members on this forum, myself included, are currently using this lower dose.

One way to gauge the effectiveness of HRT before your next DXA scan can be by testing bone turnover markers like CTX and P1NP. However, keep in mind that your CTX or P1NP levels might still be slightly elevated due to your recent ankle fracture.

In my case, I started HRT after completing Forteo. I've been monitoring bone markers and had a DXA scan 6mo after beginning HRT, which confirmed that the low dose was adequate for me and that my bmd remained stable (actually had further improvements).

In the absence of a secondary cause for osteopenia or osteoporosis, estrogen therapy is likely to prevent, or at least slow further bone loss. Past studies have shown an average improvement of 2-4% in bmd after 1-2 years of using transdermal estradiol.