User blog:God of nothing/Titan shifters-Invincible?

Ok. we all know of the regenerative abillity of the titan shifters. But what i ask here is are they actually immortal? Titan are able to survive even if their head is knocked off, but does that apply to the titan shifters in their human form too? If yes, how could they be killed? Do they have a weakpoint? I there a mini human inside of their napes?