Stress Hormones and Human Developmental Plasticity: Lessons From Tadpoles

Introduction Phenotypic expression depends on the interaction between the genotype (nature) and the environment (nurture). This is true for all living organisms, but the physiologic mechanisms that mediate this interaction remain poorly understood. Very early developmental events generally are regarded as being buffered from environmental effects (ie, they are canalized), but it is now clear that the earliest environment experienced by the embryo can shape developmental outcomes, that is, result in developmental plasticity or prenatal programming. For example, the probability of preterm birth is highly correlated with the experience of stress during the periconceptional period. Thus, fetal development tends to be more variable in timing and possibly more susceptible to environmental influences.