Prenatal programming of postnatal endocrine responses by glucocorticoids

Epidemiological studies have led to the hypothesis that a major component of the risk of diseases such as hypertension, coronary heart disease and non-insulin-dependent diabetes (the 'metabolic syndrome') is established before birth. Although the underlying mechanisms of this 'programming' of disease have not yet been conclusively determined, a reduced fetal nutrient supply as a consequence of poor placental function or unbalanced maternal nutrition is strongly implicated. It has been proposed that one outcome of suboptimal nutrition is exposure of the fetus to excess glucocorticoids, which restrict fetal growth and programme permanent alterations in its cardiovascular, endocrine and metabolic systems. This review focuses on the effects of endogenous and exogenous glucocorticoid exposure in utero on postnatal hypothalamo-pituitary-adrenal (HPA) axis activity, both in humans and experimental animals. The physiological consequences and proposed underlying molecular and cellular mechanisms are discussed. Current data indicate that key targets for programming may include not only the HPA axis but also glucocorticoid receptor gene and 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2) gene expression in a range of tissues.