Methods of determining bone mass.

Abstract

Bone disease is one of the most important clinical manifestations of primary hyperparathyroidism. Recent studies have shown that the loss of bone in "modern" hyperparathyroidism is not homogeneous throughout the skeleton. Whereas measurements of the spine and the trabecular portion of iliac crest are normal or even slightly increased, the wrist and the cortical bone of the iliac crest are significantly lower than expected. Thus, knowledge of the percentage of trabecular bone at each measurement site is important. These include distal radius, 80%; midradius, 5%; vertebrae, 19-25%; vertebral body, 33-42%; and femoral neck, 43%. Knowledge of the precision and its relationship to ranges and rates of change of bone mass are essential. For an individual, the bone mass should change by 2.8 times the precision before one can determine with 90% confidence that the change was real, not due to measurement error. Noninvasive methods of measuring bone mass that are commercially available include single- and dual-photon absorptiometry, quantitative computed tomography, and dual-energy x-ray absorptiometry. The precision of these techniques varies, with the best values reported using dual-energy x-ray absorptiometry. Research should be done to describe more completely the patterns of bone loss in this disease, including longitudinal studies on rates of loss at different skeletal sites. Studies that relate the bone mass at a particular site to fractures must be done in populations with hyperparathyroidism to see if the risk of fracture is similar to the risk in normal or osteoporotic individuals.