So he is hypothyroid and on thyroxine ?
The way he is sounds very typical. I am hypo and on thyroxine, but I have no reserves of energy and I feel nothing like how I was pre-thyroid disease. I often feel flat and struggle to have enthusiasm and energy for things.
It is better when my levels are good, but still far from “normal” .
He needs to ask what his levels are, because he may be under medicated , it is very common. He also needs to ask to be tested for coeliac, and his iron, B12, and vitamin D.
Thyroid disease gets little sympathy because people with it look fine. Everyone assumes that once you are on thyroxine you are ok again, but for very many people this is not the case at all. Auto-immune disease is in itself tiring.
I was very energetic, enthusiastic, cycled everywhere, bouncy and sociable. I am nothing like that now, even when my levels look ok my vitamin D is too low and I am struggling to improve it. I get brain fog, need quiet time alone, and after a day out somewhere, the next day I am flat, grumpy, and exhausted.
Have a look at thyroid Uk website, and think of joining for their newsletter.