Macbook Pro w/Retina - External Screen

Hi,

My Macbook Pro w/Retina overheats like crazy. It nearly get sup to 100 degrees celcius while gaming or even watching youtube. So on the thought of overheating, is it because its using a lot of power to support the Retina Display sceen? What if I hooked it up to an external screen and shut off the main Retina Screen? (Close the macbook while running on external monitor).

Thanks,
Alfrancis Guerrero