I was upgraded my MacBook Pro’s operation system from Lion X to Mountain Lion. Then i synced my iPhone 5 to the MacBook Pro using iTunes. But after that, a Personal Hotspot feature on the iPhone has dissapeared. For you guys, who get the same problem, do not a panic. Here the solution:
Normally, the Personal Hotspot feature apprear in General Page, but see, the feature has dissapered.
Open Personal Hotspot
Back to General, see Personal Hotspot has appear.