Abstract
Z-scores express differences from normals in standard deviation units, and are particularly useful for comparison of changes where normal values are age- and sex-dependent. We determinedz-scores for bone mineral mass, cortical thickness, and bone mineral density in the radius in various conditions and diseases in both sexes. In the males,z-scores were calculated for age, but in the femalesz-scores for menopausal status (years postmenopausal exclusive of years on estrogen treatment) were found to be more appropriate. With few exceptions, changes in a disease were of a similar order in both sexes. For bone mineral mass few meanz-scores were significantly increased, but diseases with significantly decreased meanz-scores were numerous. The usefulness ofz-scores in diagnosis and study of metabolic bone disease is discussed.