I think I read about that in a book I got called 'Adrenal Fatigue'. That problem can precede thyroid problems, speaking from experience. Their symptoms can be similar.I was put on thyroid meds at one time and it really didn't change me a lot. Then after 10 years of various health struggles I came across some things about adrenal fatigue and finally found a doctor who knew about it and started treating me. It will be a slow recovery, but it took me 10+ years to get in the state I'm in, so I'll have to be patient. It's a good thing I have a big interest in alternative health, otherwise I would've continued my decline.
There's a web site the author set up; www.adrenalfatigue.org.
He wrote the book to try to educate people on this since not many medical doctors address the problem until it reaches the addisons disease stage, which is when they quit working. If left untreated, it can cause many other health problems along the way. It's a book everyone should have on hand to learn how to avoid burning them out. Wish I'd had it 20 years ago!
One way to check your adrenal health is to lay down and get relaxed, then have someone take your blood pressure. Then stand up and have it taken again right away. In a healthy person, their bp will rise some, but in an adrenal fatigue person it will drop instead. That's the first test my doc did on me and his response was "boy, your really are shot!" Then he did other tests to see what my cortisol levels and other hormone levels were. When my results came back, he said I only a couple of numbers away from not being able to get out of bed, so I'm glad I found him when I did!
Any way, that's probably more than you wanted to hear, so I'll quit. I just have a big interest in how living things funtion.