Thanks so much for sharing your challenging situation with us. You are in a tough position, because many osteoporosis medications are designed for and FDA approved for postmenopausal women. Although they may be precribed for younger individuals, not as much is known about possible long-tern effects. However, considering your recent fracture history and DXA scores, it is not surprising your doctor is discussing treatment now -- at the age that would naturally be your peak bone mass -- rather than waiting for the situation to get worse

.

You didn't mention your personal situation, but if you are considering having a child in the near future,  you should know that Forteo is contraindicated (not to be given) in women who are pregnant of breastfeeding -- and if your doctor does believe this medicine is right for you, extra care should be taken to avoid pregnancy. (This may also be true of other osteoporosis medications as well.)

Also, you may want to discuss your exercise regimen with your health professional as well. There is no question keeping fit can help build stronger bones, but serious athletes (such as yourself, since you mentioned completing a half marathon) should consider taking additional steps to stay healthy. Specifically, calcium is lost in sweat, so you may need more than the recommended daily dosage (usually 1000 mg for someone your age) -- check with your doctor about whether you should increase your intake to make up for it. Also, if your exercise routine becomes so intense that you stop getting your period -- a condition that is not infrequent in serious runners -- it is a sign that your body is not producing enough estrogen to preserve your bone mass adequately. Lastly, with your fracture history, you may want to discuss with an athletic trainer or health professional if you should (at least temporarily) substitute running with a lower-impact exercise such as the elliptical machine.

Best of luck to you and please keep us posted on your progress!