Osteoporosis – the Most Common Metabolic Bone Disease

By Suhail A. Khoury, M.D., F.A.C.P., Ph.D.

OsteoporosisIt is characterized with low bone mass and deterioration of bone microstructure leading to a decline in bone strength and increased risk of fracture. It affects women significantly more than it does men. 10 to 15 million Americans have been diagnosed with osteoporosis and more than 1.7 million osteoporotic fractures occur in US annually. Consequences of osteoporosis may be devastating. These include increased mortality, pain, physical limitation, loss of independence, poor self image, and depression. The financial impact is also sizable; the estimated annual cost in US exceeds 15 billion dollars.

Risk factors for osteoporosis include genetics (such as baseline bone mass and family history of osteoporosis), previous osteoporotic fractures,  race (Caucasian, Asian), gender (female), age (more than 50) sedentary life style, smoking, excessive alcohol (more than 2 drinks per day), excessive caffeine (more than 2 cups per day).  Osteoporosis may also occur secondarily, as a consequence of other illnesses (thyroid disease,  rheumatoid arthritis, diabetes, kidney disease, some cancers,(multiple myeloma), celiac disease and others),or it may occur  due to medications (cortisone, thyroid supplements, anti-seizure drugs, immunosuppressants).

Bone is metabolically active tissue.  It is  undergoing continuous growth and repair.  Bone mass continues to build and increase from birth to about 25 to 30 years of age.  From there on, the rate of bone loss exceeds the rate of bone building, causing a slow decline in bone mass (estimated annual decline of  0.5%) until menopause, at which time the rate of bone loss increases to about 3 to 5% per year for 3 to 5 years.

Bone is an active tissue being constantly repaired from the continuous wear and tear.  Two types of cells are involved in this process:  one cell dissolves the injured tissues, the other makes new bone to replace the dissolved bone.   These two cells do not work at the same rate.  At a young age the building cells work faster and lead to increases in bone mass.  Later in life, the dissolving cells work faster and lead to net bone loss.  Many factors contribute to the numbers and metabolism of these cells. Sex hormones (estrogen and testosterone) among other factors decrease the population of dissolving cells and increase the number and activity of the rebuilding cells.  Hence with low estrogen levels, which occur at menopause, dissolving bone is accelerated and leads to net bone loss and eventual development of osteoporosis.

Multiple diagnostic methods are available to measure bone density.  The golden standard is the dual energy xray absorptiometry (DEXA) of the lumbar spine and of the hip.  Measurement of bone density at peripheral sites (heel, finger and wrist) may be used for screening, but not for diagnosis or follow-up.  DEXA is simple test, does not require disrobing, takes a few minutes, has minimal xray exposure and is inexpensive.

Bone loss is measured in standard deviations, defined as T score.  A T score of up to minus one standard deviation of bone mass is acceptable as low fracture risk.  Loss of 2.5 or more standard deviations, establishes the diagnosis of osteoporosis.  Bone loss between this range (minus 1.0 to –2.5 standard deviations) is known as osteopenia.  Other risk factors mentioned above in addition to the T score are used to calculate another parameter called the FRAX score. The FRAX algorithm gives the 10 year probability of an osteoporotic fracture and assists the Physician in treatment decisions.

Treating osteoporosis should begin with prevention; by encouraging exercise, proper nutrition, and calcium intake during the growing years.  This should continue throughout life.  The average adult requires 1200 mg of calcium daily and 1000 to 2000 units of Vitamin D daily. Weight bearing exercises are necessary in stimulating bone growth.  Fall prevention in the elderly decreases the risk of fracture.

Multiple medications are currently available for the treatment of osteoporosis.  Those may be taken orally, injected under the skin, or given intravenously to treat  osteoporosis.  All but one of these agents work by decreasing the rate of natural bone deterioration, allowing bone building to exceed bone loss leading to an increase in bone mass.  Teriparatide, (Forteo) is the only anabolic agent that works by increasing the rate of building cells.

The side effects of the available medications are rare, and  generally speaking the advantages far exceed the risks. Choosing a medication is done on an individualized basis.

Osteoporosis should no longer be accepted as an inevitable component of ageing.  We  have the knowledge and the agents to properly treat it.

Khoury Medical Institute
(941) 359-3337

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