Cortisol circadian rhythms and stress responses in infants at risk of allergic disease.

Altered hypothalamic-pituitary-adrenal function associated with allergic disease has generally been thought to be secondary to the stress of chronic disease. However, recent studies suggest that altered cortisol circadian rhythm and cortisol stress hyper-responsiveness precede the inception of allergic disease and are possible links between preventive factors associated with the hygiene hypothesis and the development of allergies. Elevated endogenous cortisol responses to stressful stimuli could predispose susceptible hosts to atopy and allergic disease by biasing the developing immune system to a T helper 2-predominant immune response, greater total and allergen-specific serum immunoglobulin E responses, and/or inhibition of peripheral immune tolerance. Because glucocorticoid receptors are present throughout the human body and many genes contain glucocorticoid response elements, variances in endogenous cortisol concentrations could have an impact on the phenotypic plasticity of a wide range of immunologically active genes during early human immune development. Here, recent findings related to hypothalamic-pituitary-adrenal function in infants predisposed to developing allergic disease are discussed along with speculation regarding the potential causal role of endogenous cortisol in the inception of allergic disease. Copyright (c) 2006 S. Karger AG, Basel.