Could hyperthyroidism be temporary? in a man?

Yes, absolutely: Hi. Hyperthyroidism can be temporary in men and women. It's called a subacute or acute thyroiditis and is self-limited, usually followed by a self-limited period of hypothyroidism, and returning to normal over a total of a few months (other courses are also possible). Your numbers definitely could that, but could be other stuff too. See an endocrinologist; they know that stuff. Good luck!