You're right,
@Richard7 -- maybe the pituitary giving up the ghost (i.e. not releasing enough ADH), since hypopituitarism is often seen in ME and CFS. Could be an HPA axis issue, where hypothalamus is not 'communicating' with pituitary clearly, so you get function in stops and starts.
I love the assumption that these people must be tired because they get up to pee. No, you morons, it's because having low blood volume means less efficient
everything. (Le sigh).
Super-rare, too.
Everything's rare if you don't test for it.
When I was first ill, it seemed every autonomic and endocrine problem one could have, I had. I had raging thirst with lots of peeing for a few days and then the symptom would go away. Happened a few times before that symptom departed for good...
-J