My husband takes synthroid, and I’ll answer as an observer. I didn’t really notice that he had more energy, he still seems tired and he sleeps very deeply. He says (and has always said) that he can’t tell the difference, but I will say that sometimes there is a delay in getting his script refilled, and when he goes without his medication I can see a huge difference in him. I can just see in his face that something is “off,” and he won’t eat for long periods of time and is very confused and just “fuzzy.” I’m not sure if this is helpful, but if my husband were answering he would likely say that he didn’t/doesn’t notice any change – but I do.