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Hypothalamic–pituitary–adrenal function during health, major surgery, and critical illness

### Key points



The basic constituents of the hypothalamic–pituitary–adrenal (HPA) axis will be familiar to most physicians because the ‘stress response’ is seen after any significant illness, injury, or surgery. However, this article seeks to highlight the substantial advances in understanding that have been made in the last decade and how these may alter treatment and guide future research.

A simple schematic of the HPA axis can be seen in Figure 1.1 The paraventricular nucleus (PVN) of the hypothalamus is the ‘control centre’ of the HPA axis. It receives input from multiple other centres: