My cousin showed me some pictures of an uncle of mine whom I hadn't seen for 5 years. So I told him "He has grown old. pay my regards to him."
And as 5jj said, "Give him my regards" would be more natural. The point being made was that it looked as if you were specifically asking for your regards to be passed on
because your uncle had visibly aged. That was the part that didn't make any sense. As long as his ageing wasn't the reason for your regards, then it's fine. I might have said "Wow, he's looking so much older than when I last saw him. Anyway, please give him my regards/send him my love".