Growth hormone receptor gene variant and mandibular height in the normal Japanese population

This study was aimed at quantitatively evaluating the relationship between craniofacial morphology and the Pro561Thr (P56IT) variant in the growth hormone receptor gene (GHR), which is considered to be an important factor in craniofacial and skeletal growth. The subjects were unrelated individuals in a normal Japanese population and consisted of 50 men and 50 women. With the use of genomic DNA extracted from whole blood, the GHR gene P56IT variant was detected by the polymerase chain reaction-restriction fragment length polymorphism method (with the restriction enzyme StuI). The relationships of the genotypes to body height and 5 linear measurements from lateral cephalograms were examined for evaluation of craniofacial morphology. The normal Japanese population without P56IT had a significantly greater mandibular ramus length (condylion-gonion) than did those with P56IT. This suggests that the GHR gene P56IT variant may be associated with mandibular height growth and can be a genetic marker for it. Further studies about such genetic markers may expand our understanding of the genetic control in craniofacial morphological determinants and help in the prediction of craniofacial growth.