Forteo Injections for Osteoporosis

Will They Prevent Fractures?

Question: My doctor told me that I am at a high risk for fractures—I am post-menopausal, have a low bone mineral density, and have a family history of osteoporosis. She mentioned Forteo injections as a possible treatment for me. Will you tell me more about this medication? Why am I a good candidate?
Parrott, GAParathyroid hormone (PTH, parathormone, parathyrin) protein, secreted by the parathyroid glands. 3D illustrationAnswer: From your history, it sounds like you have several factors that increase your risk of suffering a fracture related to low bone density or osteoporosis. Some of the causes of osteoporosis are things you don't really have control over, such as the fact that a family member had osteoporosis or that you're post-menopausal.

The key consideration for you and your doctor is what measures can be taken to minimize your risk for an osteoporotic fracture in the future. Such fractures are extremely common—it's estimated that at least 40% of all women will suffer one in their lifetime (1). To get a more specific understanding of your personal risk of suffering a fracture in the next 10 years, the World Health Organization's Fracture Risk Assessment Tool (FRAX) may be helpful.

Even more important, however, is working with your doctor to be sure other causes besides the ones you listed—so-called secondary causes of osteoporosis—are not present. Examples of secondary causes include vitamin D deficiency, excessive parathyroid hormone secretion, and excessive calcium loss by the kidney.

Once a complete assessment of your bone health has been made, you and your doctor can decide on the next step. You will certainly want to make sure that you are taking in enough calcium and vitamin D, getting enough exercise, and minimizing things that may decrease your bone strength such as excessive alcohol and smoking.

Based on your individual risk for fracture, you may also need to use medication. There are two basic categories of prescription medications for osteoporosis: antiresorptive agents, which stop the loss of bone, and anabolic agents, which cause new bone to form.

Bisphosphonate drugs, such as Fosamax (alendronate), are examples of antiresorptive drugs. They are widely used to stop the loss of bone caused by many different conditions and have been shown to reduce the rate of fractures. However, no new bone is formed by bisphosphonate treatment.

If you have a very low bone density, have had a previous fracture associated with osteoporosis, have not had success with bisphosphonate therapy, or have a very high risk for a fracture, your physician may want to build up your bone with an anabolic agent such as estrogen or Forteo (teriparatide).

Forteo is a synthetic version of your body's own parathyroid hormone. When parathyroid hormone levels are continuously high, bone strength can decline. However, when Forteo is given in daily injections, bone strength is increased, and the risk for future fracture is decreased. To learn more, read about the parathyroid on EndocrineWeb.

The risks to you of taking Forteo include high calcium levels in the blood and high calcium loss by the kidney, which could lead to kidney stones. Your doctor will monitor for these conditions while you are taking Forteo.

An additional theoretical risk to taking Forteo is developing bone cancer. Some laboratory animals treated with very high doses of Forteo developed bone cancer after years of treatment. The risk of Forteo to humans is unclear, as increased bone cancer has not been seen in the several hundred thousand patients treated so far. Even so, the FDA has recommended that patients with an increased risk for bone cancer should not take Forteo.

FDA guidelines also state that no patient should take Forteo for more than two years. Fortunately, this is long enough to have a significant impact on your bone strength. Once the treatment course is over, it is common to lock in the gains in your bone density by taking an antiresorptive medication.