[Genetic background of osteoporosis].

Osteoporosis is characterized by a decrease in bone mass as well as a deterioration of the bone architecture resulting in an increased risk of fracture. The disease is multifactorial, and it depends on environmental and genetic factors. Twin studies have shown that genetic factors account for 60-80% of the variance in bone mineral density, the best predictor of the risk of osteoporosis. There are different approaches to identify these genetic factors. Linkage studies in human and experimental animals have defined multiple loci that regulate bone mass but most of the genes responsible for this effect remain to be defined. The 11q12-13 locus was the first that was linked to bone mineral density of the young female and special bone diseases like high bone mass syndrome and osteoporosis-pseudoglioma syndrome. Both diseases appear to be in association with LDL receptor-related protein 5 gene mutation. The effect of LDL receptor-related protein 5 on bone metabolism had not been known only genetic methods suggested it. The effect of LRP5 in osteoporosis pathogenesis requires more investigation. Association and linkage studies have been performed in order to identify candidate genes in the pathogenesis of osteoporosis. Vitamin D receptor gene was the first candidate, however its effect is controversial. Other candidates, such as insulin like growth factor, interleukin-6, estrogen receptor alpha, transforming growth factor beta show no or small effect on bone mineral density or fracture frequency. To date only Sp1 polymorphism of collagen gene seems to have a consistent effect on bone fragility. The improved understanding of osteoporosis genetics should lead to better diagnosis of this disease and new treatment and prevention strategies.