Calcitonin - Protecting Your Bones: Osteoporosis

Content provided by the Faculty of the Harvard Medical School

Calcitonin

Calcitonin is approved only for the treatment, not the prevention, of osteoporosis. Generally, calcitonin is regarded as a less effective treatment because it doesn't build bone as robustly as other medications and it is unclear whether it helps prevent hip or wrist fractures.

Calcitonin, a hormone produced by the thyroid gland, helps regulate calcium by inhibiting osteoclasts. Calcitonin is also found in fish and birds, and salmon is the most common source of calcitonin used in medications. For the treatment of osteoporosis, it has been available in an injectable form since 1984 and as a nasal spray since 1995.

Although calcitonin has been tested in a large number of clinical trials and has been used to treat women with bone loss for many years, its effects are still somewhat uncertain. Women who take it usually have a slowing of bone loss or a slight increase in bone mass. It reduces the risk for spinal fractures, but hasn't been shown to lessen the risk for other kinds of fractures.

Experts have found that calcitonin is not as effective as other osteoporosis medications in building bone, and some studies indicate that the increase in bone density caused by calcitonin is temporary. This observation has led to speculation that the body may develop resistance to the hormone over time. One theory is that the body's immune system recognizes biochemical markers that identify calcitonin as having come from another species and eliminates it as a foreign substance.

Calcitonin's effect is limited to bones, so it is not linked to any other health benefits or risks. People who take calcitonin by injection generally experience more side effects than do those who use the spray. Side effects include flushing in the face and hands, dizziness, nausea, rash, and increased urination. The spray can cause a runny nose.

Last updated:	January 23, 2007