Dr. Amy Nett: That was mentioned briefly in the Week One information, and Chris is going to go into that in great detail when we do our whole unit on HPA axis dysfunction. HPA axis stands for the hypothalamic-pituitary-adrenal axis. “Adrenal fatigue” is sort of the term that is more casually used to essentially refer to HPA axis dysfunction, so in a way, they’re synonymous, but adrenal fatigue isn’t really … we don’t consider it a very precise way to explain HPA axis dysfunction because adrenal fatigue suggests that the adrenal glands have become fatigued, they’re not putting out enough cortisol, but we know that it’s such a complex relationship, and it primarily involves the hypothalamus and stress inputs that your hypothalamus is receiving.
The hypothalamus receives stress inputs. It sends a signal to the pituitary gland. The pituitary gland then sends a signal to the adrenal glands to increase cortisol production, cortisol, of course, being the major stress hormone. So HPA axis dysfunction refers to a very broad range of abnormalities in both the total amount of cortisol that’s produced and also the cortisol rhythm. So when we say “HPA axis dysfunction,” it’s just a slightly more precise way of explaining what’s otherwise referred to more commonly as adrenal fatigue syndrome. I think we just like to be a little bit more clear with our words. Adrenal fatigue syndrome just doesn’t quite fit, and it doesn’t quite describe the complexity of what we’re talking about in terms of HPA axis dysfunction.