Recovery from Running Collapse

If this happened to me and I had a similar medical condition that may or may not be to blame, I would be consulting with my physician rather than a bunch of wags on an internet discussion board.

But I'm funny that way.

Did you consult with your doctor before the event?

I'm no expert on thyroid conditions. I am however, an expert when it comes to doing stupid crap I shouldn't have done, and then going to a doctor after the fact and saying "hey can you fix this?" I've done that many times...

Probably a better approach would be a pre-emptive visit to inform your doctor of your intent to train and race, and find out what you may need to watch. As for not eating and going to hard, well... nutrition and planning (pace plan in this case) are event #4 and event #5 in triathlon (recovery is #6). Pay as much attention to those as you do to your swim, bike, and run and you racing will be better and more enjoyable...

I have hypothyroidism, too.  I've forgotten to take medication once in awhile, but that usually doesn't have much of an effect that day.  It takes a few weeks for the medication to raise levels in your blood stream and (at least in my experience) one day doesn't matter as much if it's not a regular occurrence.

Not eating is going to be huge thing.  I get very weak if I don't eat regularly.

All that being said, you should go to your doctor.  You might need to have your thyroid levels rechecked and get everything else checked out.