The striker has been linked with Celtic.
Hughton said: "Probably it is not my responsibility to say anything because I haven't made any comment on that subject. What I have seen is press speculation.
"Grant is a player who signed a new contract in the summer and he has two years left.
"I might be wrong, but I believe he started more games this season than last season so this is someone who has been right in there playing games. Anything you read or hear is speculation, because for me it is not an issue."