The role of the hypothalamic–pituitary–adrenal axis in rheumatoid arthritis

It has become clear that there is a bidirectional communication between the neuroendocrine and the immune system and that both systems influence each other and interact under physiological conditions and in response to inflammatory stimuli. The hypothalamic–pituitary axis plays an important role in regulating and controlling immune responses and dysfunction of the axis has been implicated in the pathogenesis of rheumatoid arthritis (RA). Corticotrophin-releasing hormone (CRH), one of the main hormones of the axis, is also released extra-hypothalamically, peripherally at the site of inflammation and may modulate inflammatory responses locally. In this chapter we will discuss the role of the hypothalamic–pituitary–adrenal (HPA) axis and peripheral CRH, its influences on immune function and what is known about the possible pathogenetic role of the HPA axis and peripheral CRH in RA.