Hormones as epigenetic signals in developmental programming

In mammals, including man, epidemiological and experimental studies have shown that a range of environmental factors acting during critical periods of early development can alter adult phenotype. Hormones have an important role in these epigenetic modifications and can signal the type, severity and duration of the environmental cue to the developing feto-placental tissues. They affect development of these tissues both directly and indirectly by changes in placental phenotype. They act to alter gene expression, hence the protein abundance in a wide range of different tissues, which has functional consequences for many physiological systems both before and after birth. By producing an epigenome specific to the prevailing condition in utero, hormones act as epigenetic signals in developmental programming, with important implications for adult health and disease. This review examines the role of hormones as epigenetic signals by considering their responses to environmental cues, their effects on phenotypical development and the molecular mechanisms by which they programme feto-placental development, with particular emphasis on the glucocorticoids.