Does cortisol regulate ACTH?

Question

Does ACTH affect cortisol levels, and then the cortisol levels affect the ACTH levels. Do cortisol and ACTh regulate them selves?

Answer 1

Yes, they influence each other through what's called a negative feedback system, which is very common in the body to keep things in homeostasis:

http://en.wikipedia.org/wiki/Negative_fe...

http://www.biology-online.org/4/1_physio...

ACTH stimulates the adrenal glands to make cortisol, but as more and more cortisol circulates in the blood, it inhibits the production of ACTH (by the pituitary).  As ACTH levels drop, the adrenal glands stop making cortisol.  This stops the cortisol levels from getting too high.

As cortisol gets metabolized/excreted, the blood cortisol level drops.  The inhibition on the pituitary is then lifted, causing ACTH to be made again.  ACTH then increases cortisol production.  This prevents cortisol levels from getting too low.

In reality, the hypothalamus also plays a role by secreting CRH, so it's actually a 3-level feedback system: http://www.vivo.colostate.edu/hbooks/pat...

Hope this helps.