That's partially correct...

For some people who have panic disorder, the surge in heart rate and breathing rate from exercise might trigger a panic attack (usually if they have already been getting panic attacks). It doesn't have to do with hormones, just the physical sensations, the same way deep breathing exercises trigger panic attacks in some people.

However, exercise will not randomly cause panic in people who don't already have it, and many people with anxiety can exercise all they want with no adverse effects... actually, exercise helps many people deal with anxiety.