Posted 7/22/2020 9:06 AM (GMT -6)
I would assume it's a surge of morning cortisol. Cortisol tends to be highest in the morning to get people going for their days and wake them up. When someone has some degree of adrenal fatigue, their body is hyper-reactive to a normal morning burst of cortisol. (So even if your cortisol does not test higher than average, you could be hypersensitive to it.) I experienced the symptoms you describe in times of adrenal fatigue, and it's AWFUL and I dreaded it every day.
(I know that "adrenal fatigue" is a controversial term, but I use it because most people know what I mean by it: HPA axis dysfunction, adrenal insufficiency, hormonal imbalances, etc.)
Another thought on cortisol tests: It's possible to make a normal amount of cortisol but not have it function as cortisol should. For example, if you make normal cortisol but no progesterone, then your cortisol does double-duty substituting for progesterone's jobs, effectively giving you a cortisol deficit that you can't find on a test. This is why treating the whole HPA axis is so important.