My previous assumption, based on all footage released before the Character Creation video, was that we start with 80 + (END x 5) and then increase by 5 HP per level. But looking at the new video, we can see that Todd has 158 HP at level 14, and there is no indication that this has been reduced by radiation or other means. What this suggests is firstly that HP/level is variable, and secondly that it is not retroactively increased as our Endurance level goes up. The formula I have used on http://vault111.com would mean that our HP would increase per level as follows:
END 1-3, 4 HP/level
END 4-6, 5 HP/level
END 7-9, 6 HP/level
END 10, 7 HP/level
The fact of HP/level NOT being increased retroactively would prevent us from building a low END character at the start of the game who was later able to catch up with another player who started off with, say, 10 END. The formula I have suggested also matches the Character Creation video, allowing for a starting END of 3, and an increase by 1 point at level 9. This of course assumes that the increased gain rate starts at the level at which the increase is applied. If this is not the case, then Todd would have raised his END to 4 at level 8 instead of level 9.
Hope that helps
EDIT: the suggested HP cap at level 51 would prevent us from acquiring ridiculous amounts of HP simply by levelling up due to there being no level cap. Also note, as others have stated above, this is all still speculation at this stage, but it does fit what we have seen so far.