Hyperparathyroidism and Osteoporosis

Patients who have primary hyperparathyroidism should be aware that their bone health may be affected.  This is because the high PTH level causes calcium to be gradually depleted from the bones, where almost all of the body’s calcium is stored.  This does not occur overnight, but if left untreated, it can lead to a weakening of your bones.  The calcium concentration in the bones is directly related to their density and strength.  How important is this?  Well, if your bones are not strong, you have a higher risk for broken bones, or compression fractures. This is more of an issue for women than men, because of the effect of estrogen and testosterone on bone density.  After menopause (or after surgical removal of the ovaries), women have very little estrogen production, and so there is a decrease in the stimulus for maintaining calcium influx into the bones.  In men, the continuous presence of testosterone throughout their life maintains the calcium bone levels more consistently.

Throughout our lifetime, our bones undergo a continuous process of “remodeling”.  It’s this process that allows our bones to grow bigger and longer during the formative years, and to repair themselves (with some help) after a fracture.  Up until about age 30, there is more calcium being added to the bones, than is being reabsorbed into the blood.  After age 30, there is more or less a balance between bone growth and bone reabsorption.  If anything decreases the laying down of calcium in new bone, there is a net loss of calcium in the bones, and this is how osteoporosis can occur.  In a person with severe osteoporosis, the bones are so thin that one can easily see this on an X-Ray, in that the bones will look almost transparent.  More sophisticated methods have been developed to measure the density of bones, and indirectly, the calcium level.  This is usually done with a test called a DEXA scan.  This stands for Dual Emission X-Ray Absorptiometry. “Dual” refers to using two slightly different X-Ray sources that are absorbed differently by the body and bones, and this allows a calculation to be made as to how dense the bone is.  The amount of radiation used is quite low—if you took a flight from New York to LA, you’d get about the same level of radiation exposure as for this test.

The results of a bone density test are reported as a comparison to what a healthy 30 year old would have (T-score), and a second comparison to people of your same age (Z-score).   A score of zero, would mean that your bone density is exactly what would be considered “average” for the comparison, that is either a healthy 30 year old, or the “average” woman (or man) your same age and race.  A +1 score would mean that your bone density is just at the level of being statistically significantly MORE dense than one would expect, and this would be good (the number actually refers to the Standard Deviation from the norm).  On the other hand, a -1 score means the opposite, your bone density is just at the level of being significantly LESS dense.  The actual number refers to a statistical calculation that’s not really important to understand except to say that the larger the negative number, the weaker your bones are.  By common agreement, a T score of -1 up to -2.5 is called osteopenia, and beyond -2.5 is defined as osteoporosis.  As you get older, your T score will change more dramatically than your Z score, and this is really the more important number.

Your bone density typically is measured in the specific locations where fractures most often occur, namely, at the forearm, the lower back, and along the hip bone (femur) at two places, the mid-portion or shaft, and the neck, just below the actual hip joint.  Sometimes not all of these areas are separately measured and reported.  You should be sure your test checks all these areas.  If the T score is at or beyond -2.5 in even a single location, then by definition you have osteoporosis.

It is estimated that of all women over age 50 about 20% have osteoporosis. That’s somewhere around 12 million women!!  For most of these women, the primary factor is the marked decrease in estrogen production after menopause.  There are other risk factors, including lack of exercise, weight and body build, and family history.  In addition, hyperparathyroidism is a risk factor.  Now, most of the ~20 million women with osteoporosis do NOT have hyperparathyroidism, but of those who do, the high PTH level is like adding gasoline to a fire in terms of what it does to increasing bone loss.  The same is true in men who have hyperparathyroidism, that the high PTH level will leech calcium out of the bones over time.

If you have primary hyperparathyroidism, then you WILL have an increase in resorption of calcium from your bones, and this will continue until the stimulus is removed, with a successful parathyroid operation.  If the unchecked bone resorption continues long enough, you WILL develop, first, osteopenia, and secondly, osteoporosis.  Though this may take some years, it WILL happen.  Fortunately, after correction of the high PTH level, your bones can recover much of the bone loss over time. This does not eliminate the other factors that can affect your bone density, but it would be foolish to allow the high PTH level to add fuel to the fire of bone loss for very long.

Men and women diagnosed with osteoporosis or osteopenia should definitely make sure their serum calcium level is in the normal range.  If it is elevated about 10 mg/dl, a PTH level should be ordered (and a calcium level should be repeated at the same blood draw).

So why is this important?  Well, although breaking a hip or a forearm does not seem as ominous as being diagnosed with a cancer, statistics show that fractures due to osteoporosis, actually cause just about as much trouble for women as cancer.  A hip fracture can often rob a women of her ability to care for herself as she did before, or require nursing home care.  Those who have one fracture due to osteoporosis are at greater risk to have another, with gradually snowballing effects on one’s health.  Of course not all women with osteoporosis will break their hip or forearm or other bone, but they are definitely more vulnerable.  And there are a surprising number of women who ultimately die as a direct or indirect consequence of a fracture, resulting, in turn, from osteoporosis.

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