A Gradient of Potential for Modifying Craniofacial Growth

This review evaluates the hypothesis that a skeletal structure's response to epigenetic and environmental stimuli is directly proportional to its maturity status. We focus on the craniofacial complex because it exhibits a wide growth maturity gradient and is, therefore, ideally suited to test the hypothesis of differential response potential to the same stimulus across structures. Because it is a major epigenetic factor controlling somatic growth and maturation, emphasis is placed on studies pertaining to growth hormone (GH) deficits/supplementation. GH deficiency has profound effects on overall body size/maturation and it produces characteristic abnormalities in the craniofacial complex. Human and, especially, animal studies, show that (1) the various components of the craniofacial complex exhibit substantially different response potentials to hormonal deficits, (2) growth deficits associated with GH deficits are greatest for the most mature structures; less mature craniofacial structures display the greatest potential for future growth deficits, and (3) the less mature structures have the greater potential for catch-up following GH supplementation. We conclude that the craniofacial growth maturity gradient provides a basis for better understanding variability in response potential across craniofacial structures.