To the average person, Hokage was a title of respect. If one were even lucky enough to meet the Hokage in person, one referred to her (or him, in previous years) as Hokage-sama or, at the very least, Hokage-dono. Even other Kage and jounin-oyabun used the title of Hokage-san.
Moreover, in order to become Hokage in the first place, one must be such a respected ninja that one would be accorded respect even without the title. In the case of Godaime Hokage, Tsunade had been renowned as one of the Densetsu no Sannin, the Three Ninja of Legend. She was the master slug summoner, able to summon Katsuya herself and speak with her on equal terms, as well as the greatest medic-nin on the planet and, possibly, the strongest woman in history. Accordingly, most who were not already too scared by her reputation to speak to her at all, let alone refer to her by name, called her Tsunade-sama. Among the few exceptions were her two apprentices, Shizune and Sakura—who called her Tsunade-shishou, as was only appropriate for apprentices to their mistress and those who were particularly close to her (or old enough to remember) who called her Tsunade-hime in honor of her kinship with the Shodaime and Nidaime Hokage.
And Naruto, who persisted in calling her “Tsunade-baachan.” The nerve! Not just one of her subordinates, but a genin, no less, one of the least experienced ninja in the village! (And one who would probably never become a shinobi, at that; not with that loud mouth of his.) Not even baasan, but baachan! At least it was a little better than Tsunaede-baba... Though, come to think of it, hadn’t he called her that as well?
“You know, Naruto,” she said for what felt like (and probably was) the thousandth time, “you really should show me more respect, as your Hokage, if not as a person. You’re always harping on about how much respect people give the Hokage, but you never do it yourself.”
“Hmm.” Naruto seemed to think for a moment. “You may be right...” Tsunade let him think, pleased that either the repitition or the way she had phrased it this time had made an impact. Maybe she wouldn't have to kill him before he made chuunin after all.
“Yeah, you’re definitely right. I should address you more respectfully. Hokage-chama!”
Lying on his stomach that night, preparing to go to sleep, Naruto idly wondered just how many people knew the Thousand Years of Pain technique. And if he could come up with a version that would work on females.
Okay, time for notes. First off, I'm sure you all know just how important honorifics are in Japan. I start with a sort of explanation of some of them, but here's a more direct list: sama is a term of great respect; dono is slightly less respectful (though in an archaic usage it's more respectful, meaning literally “lord”); san is a term of respect among equals; hime means princess and, in Tsunade's case, refers to the fact that she is the granddaughter of the First and the niece of the Second; shishou means mistress; baachan means granny; baasan means grandmother; baba means old hag. And, for the grand finale, chama is a term of respect (taken from sama as chan is taken from san) for someone very old. And, yes, I meant to have that line in there about Naruto not being a shinobi; shinobi literally means "spy," a profession I doubt Naruto will be successful at. Ninja, on the other hand, is a contraction of nindosha, literally "one who practices the way of the ninja," which Naruto—quite vocally—is. Incidentally, the suffix -ka can be exchanged for -sha/-ja, changing the meaning from a practitioner to an expert (thus, I am a rather crappy mangasha, while Kishimoto is an accomplished mangaka); I imagine that one could articulate Naruto's dream as becoming worthy of being known not as a ninja, but as a ninka (or nindoka).