Lupus and Osteoporosis: A Rheumatologist’s Perspective

1. Introduction
2. What is osteoporosis? What is osteopenia?
3. What is bone?
4. Assessing and Diagnosing Osteoporosis
5. Predisposition to Osteoporosis
6. Treating Osteoporosis
7. Conclusion

Only within the past few years have researchers began studying osteoporosis in lupus patients. These studies have shown, however, that many patients with lupus have an increased risk of osteoporosis. For instance, recent studies have estimated that the incidence of osteoporosis for lupus patients is between 4 and 23%, and the estimated incidence of osteopenia in lupus patients is between 25 and 46%. Lupus patients have an increased risk of osteoporosis for many reasons. Lupus itself seems to increase the risk of osteoporosis. In addition, certain medications used to treat lupus may be associated with bone loss. Additionally, lupus patients often are unable to exercise regularly.

Osteoporosis is a systemic skeletal disorder. People with osteoporosis have low bone mass and a deterioration of the bone in the sense that their bones are not as strong or thick as they once were. Osteoporosis increases the risk of breaking a bone because the bones are more fragile and susceptible to fracture. Osteopenia is characterized as bone mineral density that is lower than normal, but not low enough to be diagnosed as osteoporosis. Bone mineral density is the measure of the level of the minerals in the bones indicating how strong or dense they are.

Bone is composed of two things – matrix and mineral. Matrix is primarily the collagen in the skeleton, and the mineral is made up of calcium and phosphorus. The body wants to keep a certain amount of calcium in the body so all of the organs in the body work properly. If the calcium levels decrease for any reason, the body sends out a signal and takes calcium out of the bone to maintain enough calcium in the blood. As a result, the bones become weaker.

There are two types of bone in the body. Cancellous bone, also known as the trabecular bone, has a large surface area and is “honeycombed” with a lattice structure; an example is the vertebrae. Cortical bone, also known as the compact bone, is denser than the trabecular bone; an example is the outer hip. Most treatments for osteoporosis work better on the trabecular bone than on the compact bone. Once a lot of bone has been lost, it can never really be replaced. Although the medications can help, the bones will never be as good or strong as they once were.

There are two main types of cells in the bone – the osteoblast and the osteoclast. The osteoblast cell makes new bone; the osteoclast cell breaks down the bone and resorbs it.

The World Health Organization (WHO) has developed a set of criteria for assessing disease severity of osteoporosis. A bone density test is used for assessing osteoporosis by scanning the body and reporting on the strength of the bone in the lower back, hip, and sometimes the wrist. The T-score is used to compare a patient’s bone density to the bone density of a young, healthy, 30 year old male or female of the same ethnicity. A T-score between 0 and -1 standard deviations below young normal control is considered normal, a T-score between -1 and -2.4 standard deviations below a young normal is considered osteopenia, and a T-score -2.5 or more standard deviations below a young normal is considered osteoporosis.

There are several diseases and conditions that predispose a person to osteoporosis:

• Thyroid Disease (i.e. overactive thyroid)
• Malabsorption (nutrients are not absorbed well in the body)
• Inflammatory Diseases (i.e. Lupus or Rheumatoid Arthritis)

There are also several medications that predispose or may cause osteoporosis:

• Steroids
• Lithium
• IV Heparin

In addition, there are also certain risk factors for osteoporosis:

• Personal history of a bone fracture as an adult
• Weigh less than 127 pounds
• Tobacco use
• Alcohol abuse
• Post-menopausal status
• Low calcium levels
• Low vitamin D levels
• Caucasians and Asians are more likely to be diagnosed with osteoporosis, as are women in general

Lupus patients have additional risk factors for osteoporosis that are specifically related to their disease:

• Lupus flares
• Active lupus
• Onset of lupus prior to age 30 (age of peak bone mass)
• Limited sun exposure
• Chronic glucocorticoid use
• Therapy-related early menopause (i.e. cytoxan)
• Medications (i.e. anticonvulsants, heparin) which are associated with low bone mass

The most common medications prescribed to treat osteoporosis are the bisphosphonates, which include Actonel, Fosamax and Boniva. These three medications, taken orally, reduce bone loss and fracture risk. A newly self-injectable medication called Forteo also improves bone density and reduces fracture risk. As with most medications, there are side effects, and patients are encouraged to talk to their doctor about any side effects from medications.

Patients should also have between 1200-1500 mg of calcium a day, either through diet or supplements, and about 800 IU or more of vitamin D daily. Exercise is also extremely important and critical in preventing bone fractures.

In summary, it is important for lupus patients to get enough calcium and vitamin D, exercise as best they can, get a bone density test every one to two years, and discuss additional treatment options with their doctor.

Learn more about HSS’ SLE Workshop, a free support and education group held monthly for people with lupus and their families and friends.