Osteoporosis is the condition in which the bones have a lower calcium content than normal.  This causes them to be susceptible to fractures.

Each of us lives in a precarious balance between the amount of calcium we take in through our diet and the amount of calcium we loose each day in our urine.  Calcium is needed to maintain the strength of the bones and the skeleton.  This is done through hormone action that lays down calcium phosphate crystals within a net-like matrix of cartilage.  If the loss of calcium exceeds the intake, the bone level of calcium progressively declines.  This causes the bone to become progressively less dense, progressively weaker, and progressively more prone to fracture.  Factors that contribute to bone loss are:  inadequate calcium intake, loss of hormone support (menopause), child birth, breast feeding, smoking, steroid administration, kidney disease, and immobilization.  Factors that contribute to bone calcification (bone build up) are: ample calcium intake, estrogens, and weight bearing exercise.  In addition, the smaller your bones, the sooner that bone loss will reach the critical point of fracture susceptibility.

Although the disorder involves calcium, there is no lab test for the specific diagnosis of osteoporosis. The most important diagnostic tool is a measurement of the Bone Density performed by a Densitometer.  This is not a lab test – it is carried out by Medical Imaging (X-ray) labs and a variety of private mobile testing units.

The clinical lab can provide useful adjunct information.  If severe osteoporosis is diagnosed then lab testing may reveal the cause.  For example, a depressed TSH will indicate that hyperthyroidism is present and this is known to be a cause of osteoporosis. A PTH test may indicate the presence of Hyperparathyroidism – a rare cause of osteoporosis.

The lab does offer bone marker tests that tell whether bone is decalcifying or whether it is building up. The measurement of Osteocalcin is correlated with bone formation and is low when bone is not forming at the correct rate.  The measurements of either Deoxypyridinoline Crosslinks or N-Telopeptide can be used to assess how rapidly bone is dissolving.  These tests can be helpful in determining whether treatment for osteoporosis is effective.