Osteopenic syndromes in the adolescent female.

Low bone density in growing girls and mature young women is usually a finding that needs an explanation and further clinical investigation. Population-based epidemiologic studies on osteoporosis in young persons do not exist. As a disease, osteoporosis among children and adolescents is rate, and since 1965 only 100 cases of idiopathic juvenile osteoprososis have been reported. When osteoporosis occurs in children, it is usually secondary to an underlying medical disorder (e.g., anorexia nervosa, leukemia) or to medications, but occasionally no identifiable primary cause can be detected. It may also be the result of a genetic disorder such as osteogenesis imperfecta. On the other hand, osteopenia in growing and young persons seems much commoner and needs further investigation. Adolescence is a period of increased calcium requirement, and girls with an underlying bone disease are at higher risk for bone demineralization. An additional point of interest is the changes in the geometry of bones through their continuous adaptation to simultaneous skeletal and muscular growth. Bones, through the mechanostat mechanism, adapt to mechanical loading by differentiating their geometry. A recent finding in this direction is that before and during the teenage years there is an environmental effect of physical activity and nutrition on hip geometry. Another important finding is an age-dependent increase in bone cross-sectional area and bone strength index in the absence of an increase in volumetric spongiosa bone density and cortical bone density. Girls, in comparison to boys, deposit more calcium in their bones during puberty, thus probably preparing their skeleton for the forthcoming events of pregnancy and lactation.