Osteoporosis: A Battle of the Bones

by Hong S. Lee, MD, and Pauline M. Camacho, MD, FACE

Osteoporosis [os-tee-oh-puh-ROW-sis] is a disease of bones that leads to low bone mass, increased bone fragility, and broken bones (fractures). Approximately 44 million Americanss age 50 and over (55% of Americans in this age group), have osteoporosis or low bone density that can lead to fractures. Of special concern are hip and spine fractures. People with a broken hip almost always need to go to the hospital and have major surgery. About 50% of patients with a hip fracture can never walk again without help, and 25% need long-term care. Spinal or vertebral [ver-TEE-bruhl] fractures are also serious and can cause loss of height, severe back pain, and deformity. Osteoporosis is most common in women after menopause. This is because bones break down without estrogen and new bone doesn’t build up as much. But osteoporosis may also develop in men. Osteoporosis may occur in anyone with hormonal disorders, such as an overactive thyroid gland or overactive parathyroid gland. Osteoporosis can also be caused by medications such as steroids (prednisone), certain blood thinners (Coumadin [warfarin]) and anti-seizure medications.

Why Osteoporosis Occurs

In normal bone, the bone constantly rebuilds itself. Bone gets absorbed or broken down by cells called osteoclasts [OS-tee-oh-klasts]. Other cells called osteoblasts [OS-tee-oh-blasts] cause the bone to form. They follow osteoclasts and lay down new bone at the site. Osteoporosis is caused by an imbalance between bone breakdown and bone formation.

Denosumab: A New Therapy for Osteoporosis

Bisphosphonates [bis-FOS-fuh-nates] have been the main treatment for osteoporosis since alendronate [uh-LEN-dro-nate] (Fosamax) was introduced to the U.S. in 1996. Since then, other bisphosphonates have become available, including risedronate [rih-SEH-droh-nate] (Actonel), ibandronate [eye-BAN-droh-nate] (Boniva), and zoledronic [zoh-leh-DROH-nik] acid (Reclast). They are different in their strength, how often they are taken, and how they need to be taken (by mouth or through the veins).

A new medicine, denosumab [de-NO-soo-mab] (Prolia) was approved by the United States Food and Drug Administration to treat osteoporosis in women after menopause who:

  • have a high risk for broken bones
  • cannot use another osteoporosis medicine, or other osteoporosis medicines did not work well.

This is a new type of medication for osteoporosis treatment. Denosumab is a human antibody made by one type of immune cell. For the last two decades, human (monoclonal) antibody has been used for inflammatory [in-FLAH-mah-toh-ree] diseases and cancers, including leukemia, lymphoma, asthma, Crohn’s disease, and rejection prevention for kidney transplants. Denosumab halts the growth of osteoclasts and keeps bone loss from happening.

In a study of almost 8,000 patients, denosumab reduced the risk of new spine fracture by 68%. It also lowered the risk of hip fracture by 40%. Treatment with denosumab also greatly increased bone mineral density (BMD) after the patients were treated for three years. Denosumab is injected under the skin (like insulin) in the upper arm, upper thigh, or abdomen every six months.

Side Effects

The most common side effects of denosumab are joint pain, inflamed nose and throat, back pain, headache, and arm and leg pain. An inflamed pancreas may also occur. Denosumab can cause serious side effects. These include low calcium level, serious infection, skin problems, and severe jaw bone problems. People with kidneys that are not working normally are more likely to end up with a low calcium level. Since denosumab is a human antibody, it may affect the immune system. Patients with immune systems that are not working normally or those on immunosuppressant [ih-mune-oh-suh-PREH-sent] agents (like those used for cancers, rheumatoid arthritis, and Crohn’s disease, for example) may have a higher risk for side effects. Lastly osteonecrosis [ah-stee-oh-neh-CROW-sis] of the jaw, or “dead jaw,” is a rare but serious side effect. It occurs when there is a loss of blood flow to the jaw. This leads to death of the tissue and collapse of the jaw bone. It can occur on its own, but it usually happens when a tooth is pulled or if there is a local infection that takes time to heal. Your doctor and also your dentist should examine your mouth before you start denosumab.

If you are considered for this treatment, make sure to tell your doctor if you:

  • Have low blood calcium
  • Cannot take daily calcium and vitamin D
  • Had parathyroid or thyroid surgery (glands located in your neck)
  • Have been told you have trouble absorbing minerals in your stomach or intestines (malabsorption [mal-ab-ZORP-shun] syndrome)
  • Have kidney problems or are on kidney dialysis
  • Plan to have dental surgery or teeth removed
  • Are pregnant or plan to become pregnant
  • Are breast-feeding or plan to breast-feed

In summary, osteoporosis is very common and can cause many serious problems. You and your doctor can determine what treatment is right for you!

Dr. Hong S. Lee is a fellow of endocrinology and metabolism at Loyola University Medical Center, Illinois. He received his doctoral degree at University of Minnesota Medicine School and finished post-graduate training at Loyola University Medical Center. His clinical interests include bone health and hypogonadism.

Dr. Pauline M. Camacho is an Associate Professor of Medicine at Loyola University Medical Center and Director of the Loyola University Osteoporosis Metabolic Bone Disease Center. Her clinical endocrine practice and research is focused on osteoporosis and metabolic bone disorders. She has had two books published: Osteoporosis: A Guide for Clinicians (published in 2007) and Evidence Based Endocrinology (latest edition published in 2006). Dr Camacho is on the national board of the American Association of Clinical Endocrinologists (AACE), and is on the Editorial Board of Endocrine Practice and the Journal of Clinical Densitometry.