As women age and enter into menopause the hormonal changes they experience causes them to suffer from loss of bone mineral density (BMD). Men who are on a hormone blockade also experience similar losses of their bone density.

Lower bone mineral density greatly increases your general risk of breaking bones. Breaking bones not only creates a major inconvenience as well as significant pain, it can also be life threatening.

As soon as you start a blockade, speak with your doctor about monitoring your BMD. Dual energy X-ray absorptiometry (DXA, previously DEXA) is the most common and least expensive means of measuring your bone mineral density. The DXA scan works by using two X-ray beams with differing energy levels that are aimed at your hip and forearm. Then mathematically the soft tissue absorption rate is subtracted out and the BMD is determined from the absorption of each beam by the target bone.

A T-score of -2.5 or less is indicative of osteoporosis. BMD scores are compared to reference data form others of the same gender and age by calculating a Z-score (a standardization of the T-score).

Most doctors are not aware that there are other variables, in addition to your age and sex, which confound the interpretation of BMD as measured by a DXA scan. Differences in bone size is not taken into consideration when T-scores are calculated.

DXA scans have been shown to overestimate the bone mineral density of taller men and underestimate the bone mineral density of smaller men. This error is due to the statistical method that the DXA scan uses to calculate BMD. In DXA, bone mineral content (measured as the attenuation of the X-ray by the bones being scanned) is divided by the area (also measured by the machine) of the site being scanned.

However, despite the statistical problems it is still a fairly accurate measure of bone mineral content. Other imaging technologies such as Computed Quantitative Computer Tomography (QCT) is also capable of measuring the BMD, but they are not susceptible to the statistical error that