The Origin of Glucocorticoid Hormone Oscillations

Citation: Walker JJ, Spiga F, Waite E, Zhao Z, Kershaw Y, et al. (2012) The Origin of Glucocorticoid Hormone Oscillations. PLoS Biol 10(6): e1001341. doi:10.1371/journal.pbio.1001341

Glucocorticoid steroid hormones, such as cortisol and corticosterone, provide a rapid response to both physical and psychological stress, and act on areas of the brain that influence learning, memory, and behaviour. Glucocorticoids are released from the adrenal glands in near-hourly pulses, which results in oscillating glucocorticoid levels in the blood and in target organs. These hormone oscillations can become disrupted during ageing and in stress-related disease (e.g., major depression), so it is important to identify the underlying mechanisms that govern their dynamics. Although the origin of the oscillations is not known, it is assumed that they are generated by a neuronal “pulse generator” within the brain. In a study published in PLOS Biology, data is presented that challenge this hypothesis. The authors characterize a peripheral hormonal system and show that constant levels of corticotrophin-releasing hormone can induce and regulate hormone oscillations independent of the brain. They also describe mechanisms that can disrupt these oscillations. These findings have important implications for our understanding of glucocorticoid signalling in both health and disease, and will be important for the design of novel treatment strategies that take into account timing of hormone administration to patients undergoing steroid therapy for inflammatory or malignant disease.