Have a google about
adrenal exhaustion.
It is quite a common concept in Chinese medicine.
As far as I know, it sometimes happens to certain individuals after a period of prolongued stress. It doesn't mean that there is anything WRONG with the adrenals necessarily. More that they are tired after a period of over use, and need a rest, and will recover with time.
Can't give more details from memory, but you may find it interesting to do the research yourselves.
Although, of course, I don't think it is recognised by Western Medicine, and I may be barking up the wrong tree.
I had it diagnosed in me about 20 years ago by a lovely alternative practitioner my mother sent me to. He suggested vitamin supplements and a few dietary suggestions, but I cannot for the life of me remember the details. The symptoms went away shortly after, and I haven't given it a thought since.