Hi Sadie:  I took Forteo for 2 years and did really well on it.  Read the link Larry gave you from the Cleveland Clinic, since it gives a great easy-to-understand explanation of how Forteo works.

Here's a link to Eli Lilys pdf on Forteo which lists all of the side effects seen in the clinical trial.  Forteo may raise your calcium and vitamin D-125 by 19% and lower you D-25 also by 19%, but this was only seen in a small group of people.  If you decide to take this have these levels checked prior to taking it and during the treatment.  My calcium/D-125 went up slightly and my D-25 went down also slightly, but my scores were like this prior to the first injection so the Dr couldn't say that Forteo was the cause, but that it may have made it slightly worse.  When I finished Forteo these three levels reverted to normal.

Good luck deciding what to do.  My scores improved fantastically, and I just hope they are still as good on my next dxa.  I went from severe osteo to osteopenia (hip) and normal bone density (spine) within the first year of treatment.  I also had my bone markers checked regularly to see if the Forteo was working.  Here's a link on that test that I wrote a blog about, that will tell your Dr how Forteo is doing in between dxa's.