Consequences of Early Life Programing by Genetic and Environmental Influences: A Synthesis Regarding Pubertal Timing.

Sexual maturation is closely tied to growth and body weight gain, suggesting that regulative metabolic pathways are shared between somatic and pubertal development. The pre- and postnatal environment affects both growth and pubertal development, indicating that common pathways are affected by the environment. Intrauterine and early infantile developmental phases are characterized by high plasticity and thereby susceptibility to factors that affect metabolic function as well as related reproductive function throughout life. In children born small for gestational age, poor nutritional conditions during gestation can modify metabolic systems to adapt to expectations of chronic undernutrition. These children are potentially poorly equipped to cope with energy-dense diets and are possibly programmed to store as much energy as possible, causing rapid weight gain with the risk for adult disease and premature onset of puberty. Environmental factors can cause modifications to the genome, so-called epigenetic changes, to affect gene expression and subsequently modify phenotypic expression of genomic information. Epigenetic modifications, which occur in children born small for gestational age, are thought to underlie part of the metabolic programming that subsequently effects both somatic and pubertal development.