Obviously you're on a laptop, so make sure it has the appropriate ventilation, i.e. at least 30-60cm behind and each side. Laptops, because the components are so close together produce lots of heat. And as the fans have to be generally side mounted, they don't push out too much air. The ambient temp around your laptop will play a big part too. My laptop with a measly 5470 will send the fans stupid if i'm sitting in bed and the rear is blocked by my fluffy blanket haha
Your graphic card will throttle back to prevent overheating...making your game run slower.