Steroid-induced Secondary Osteoporosis

Osteoporosis can be classified into two categories—primary and secondary. Primary osteoporosis, the most common form of metabolic bone disease, is a disorder of the elderly—the result of the cumulative impact of bone loss and deterioration of bone structure that occurs as people age. Alternatively, secondary osteoporosis is usually caused by diet, lifestyle and/or specific drugs.

Steroids are the most common cause of drug-induced osteoporosis. The connection between steroid-induced osteoporosis and spinal problems underscores the importance for physicians to develop care plans that address all aspects of a patient's condition, especially for patients taking steroids.

What are corticosteroids?

Corticosteroids are medicines that are similar to the natural hormone cortisone produced by the adrenal cortex (glands above the kidney) and belong to the family of compounds called steroids. Steroids are a large family of chemical substances comprised of many hormones and are used to treat several types of medical conditions.

Corticosteroids are used as treatment in a variety of medical conditions including:

• Asthma
• Inflammatory joint disorders (such as arthritis)
• Chronic obstructive pulmonary disease (COPD), a progressive disease which is commonly a result of smoking and causes wheezing and coughing
• Various diseases affecting the central nervous and gastrointestinal (stomach or intestine) systems

How do steroids cause osteoporosis?

Steroids affect bone in two ways. Steroids contribute to increased osteoclast activity (bone breakdown) and inhibit osteoblast formation (bone-building). Secondly, steroids interfere with the absorption of calcium in the small intestine. The body needs calcium to function, so when it cannot absorb enough through the gastrointestinal system, the body seeks out calcium from the bones where it is stored.

• Increased bone loss is a result of decreased calcium absorption and increased urinary calcium excretion (loss) caused by corticosteroids.(1) Supplementation with calcium and vitamin D or an activated form of vitamin D should be offered to all patients receiving glucocorticoids.(1,4)
• Abundant pseudo callus (tissue that forms in the bone in the early stages of the healing process) that forms at the site of a fracture is a strong indicator of corticosteroid-induced osteoporosis; it is most frequently found at the endplates of collapsed vertebrae.(1)

What is the connection between corticosteroids and osteoporosis?

• Bone loss occurs soon after corticosteroids initiation and is greatest in the first year (average of 5% loss).(1)
• It is estimated that bone fractures occur in 30-50% of patients who undergo corticosteroid therapy.(1)
• Corticosteroid use raises the risk of fracture six-fold across all ages, regardless of bone mass prior to steroid treatment.(3)

Studies have shown that the use of corticosteroids increases the risk of developing osteoporosis. Additionally, there appears to be a close relationship between doses of corticosteroid and the rate of bone loss, which increases the risk of vertebral and hip fractures. Significant trabecular bone loss occurs with doses of prednisone (a synthetic corticosteroid with anti-inflammatory and antiallergic activity) greater than 7.5 mg per day and occurs even with inhaled steroids.(1) Even with doses equivalent to 2.5-7.5 mg, there is an increased risk of vertebral and hip fractures.(2)

What is the risk of developing a spinal fracture when undergoing corticosteroid therapy?

The risk of having a vertebral fracture can be as high as 15% in the first year of treatment with corticosteroids.(4) Spinal fracture incidence is increased more than two-fold in patients on oral corticosteroid therapy; however, there is a sharp decline in fractures after cessation of oral corticosteroid use.(2)

For additional information about steroids and osteoporosis visit:

• http://www.nof.org (National Osteoporosis Foundation)
• http://www.spine.org (North American Spine Society)
• http://www.lungusa.org (American Lung Association)