TIMING AND GENETIC RAPPORT BETWEEN GROWTH IN SKELETAL MATURITY AND HEIGHT AROUND PUBERTY - SIMILARITIES AND DIFFERENCES BETWEEN GIRLS AND BOYS

We have analyzed longitudinal twin data by using a multivariate normal model to identify and quantify genetic effects over time on two main aspects of growth, height and skeletal maturity. The largest genetic c ontribution to the variance in both height and skeletal maturity coinc ided with the respective ages of peak growth velocity, The highest gen etic covariance between these two traits coincided with the age of gre atest acceleration of growth in height. These findings imply the exist ence of regulatory or structural genes that influence growth in both h eight and skeletal maturity. We also found sex differences in the rapp ort between velocities for height and skeletal maturity. These are con sistent with a predominant role of estrogen in accelerating skeletal m aturation in females, and the existence of additional mechanisms in ma les which may promote growth in height independently of the effects of gonadal sex steroids.