P561T heterozygous missense mutation in the growth hormone receptor(GHR) is a candidate genetic polymorphism (single-nucleotidepolymorphism) for human mandibular growth. The purpose of thisstudy was to assess whether this mutation affects mandibulargrowth during early childhood. The difference in mandibulargrowth between P561T heterozygous and wild-type individualswas analysed by cephalometric measurements during childhood.The subjects included 33 children with mandibular protrusion(aged 3–12 years, 16 males and 17 females) and 27 normalchildren (aged 3–13 years, 14 males and 13 females). GenomicDNA extracted from buccal epithelial cells was genotyped forthe P561T heterozygous mutation with a molecular analysis (polymerasechain reaction—restriction fragment length polymorphismmethod). Two of the patients with normal occlusion and fivewith mandibular protrusion were heterozygous for the mutation.
Chi-square analysis showed that the frequency of this mutationdid not differ statistically between the normal and mandibularprotrusion subjects. Multilevel model analysis of the 101 cephalogramsshowed that the mutation reduced the linear measurements ofthe mandible. These findings suggest that P561T heterozygousmutation affects mandibular growth during early childhood, andthis mutation in the GHR gene is hypothesized to function asan inhibitory factor in the process of mandibular growth.
