Pituitary-adrenal axis

In medicineand physiology, the Pituitary-adrenal axis, also termed the Hypothalamus-pituitary-adrenal axis, is the hormonalsystem of which the effectororgan is the adrenal cortex.

Adrenal and pituitary

The adrenalcortexproduces cortisolin response to stimulation by corticotropin(or: ACTH, adrenocorticotropic hormone). The pituitary gland, specifically the corticotroph cells, sense the bloodlevels of cortisol. If the levels are too low, more ACTHis secretedand the cortical activity is increased.

The hypothalamus

The hypothalamuscontrols the rate at which the corticotroph cellsrespond. In acute illness, higher cortisollevels are needed (see adrenal insufficiency). This is achieved by the hypothalamussecreting higher levels of CRH(corticotropin releasing hormone) into the portal system. This stimulates the corticotroph cellsto a higher set point, leading to increased ACTHand cortisollevels.

Regulation at hypothalamus level

Now what controls the hypothalamus? This can be stressof emotional or physical nature; the CRHpulse rate (it is secreted in pulses; the rate determines its function) is increased in response to systemic inflammation, namely IL-1, IL-6and TNFalpha.

See also

• Cushing's syndrome
• Adrenal insufficiency
• Addison's disease
• glucocorticoids
• cortisol
• dexamethasone
• hydrocortisone

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Pituitary-adrenal+axis Wikipedia article Pituitary-adrenal axis.