Higher than 600.
Some races can start the game with as much as 65 END depending on birthsign and favored attributes. Which means END can be maxed by level 8. That's only one factor, though.
EDIT: Actually, I'm gonna cede the floor to the next questioner - I'm really tired, and can't hang around to validate responses for much longer. I was up really early this morning, and my body is crying out for sleep now.
The correct answer, according to my calculations, was 738 health (achieved at level 56).