Studies on the potential mediators of skeletal changes occurring during puberty in girls

In this study we evaluated the role of cytokines and insulin-like growth fa ctor (IGF) system in mediating the skeletal changes that occur during puber ty by determining the relationship between serum levels of cytokines and IG F system components vs. 1) bone formation and resorption parameters in seru m and urine, 2) bone density, and 3) metacarpal bone indexes in 65 pubertal girls. Lumbar bone mineral density and metacarpal width increased signific antly both between Tanner stages (TS) II and III and between TS III and TV, whereas metacarpal length and serum levels of stimulatory IGF system compo nents increased significantly only between TS II and III. Biochemical marke rs of bone turnover were significantly less in TS IV girls than in TS II an d III girls. In general, serum levels of IGF system components showed a sig nificant positive correlation to bone density in TS II and III girls, where as bone resorption markers corrected for creatinine showed a significant ne gative correlation to bone density in TS III and TV girls. Serum levels of IGF system components showed a significant positive correlation to serum os teocalcin levels as well as metacarpal width in TS II girls, whereas urinar y levels of bone resorption markers showed a significant negative correlati on to metacarpal width in TS ni girls. Serum levels of interleukin-6 were d ecreased during late puberty and were negatively correlated with bone densi ty in TS III and TV girls. Our data are consistent with a model in which th e sex steroid hormone-induced increase in the IGF system leads to an increa se in longitudinal growth and periosteal bone expansion, whereas the sex st eroid hormone-induced reduction in bone turnover (possibly via cytokines) l eads to an increase in cortical thickness via endosteal regulation.