@janflute not a single human has gotten cancer (sarcoma) from Forteo. So it has been deemed safe to extend treatment. The more pertinent question, I think, might be whether it is still working to grow bone (Tymlos may have stopped building bone for me before 18 months, according to bone markers) or whether it is at least maintaining bone density/quality. I continued on Tymlos for the full two years regardless of those bone marker tests, and both my doctors suggested that it might still be of benefit. I am not sure that there are enough studies on this as yet.

Some of us are doing the two years, then a bisphosphonate to "lock in" gains, and then hope to do a bone builder again later.

@janflute,
I hope to be taking Forteo for at least three years. I may have to see your doctor. When Forteo first came out the endocrinologist I see now told me that it was the the genetics of the rats that caused the cancer. The FDA's caution was good, but forced Lily to conduct ongoing studies. The removal came after 23 years of investigation. I trust the removal.
I also find it interesting that you will be taking Fosamax and Calcitonin. Calcitonin to lower serum calcium? that is in the normal range. Foxamax and Calcitonin work in the same way to reduce the osteoclastic activity which reduces serum calcium. Basically the bones aren't breaking down and releasing their calcium into the bloodstream. Some people on Fosamax experience low serum calcium. I'd probably want to wait the calcitonin until a blood draw after a month of Fosamax
Other than that I think you have luck with your medical provider. I like that they orderd abdominal imaging to find out "what else it could be." You don't want the radiation exposure, but would you consider a colonoscopy or pill scan.
And would you take a fourth year of Forteo if the third shows more gain?