Chances are, it is running at 100% or close to. Even if you're running a discrete GPU, it's sharing a heatsink and fan with the CPU, so when you load it, as in gaming, the fan is going to ramp up to accomodate the increased heat produced. You may have an option in your BIOS to turn it down or select a less aggressive fan profile, but I don't think that it would be a good idea - laptops in general are a challenge to properly cool, and even with fan or fans maxed, you usually have to accept a higher temperature level than you would accept in a desktop.
If your BIOS gives you the option (probably not), you can try reducing your voltages to the minimum required to run your current performance levels while maintaining system stability...