It could very well be that IF, as practiced, typically does not include enough time for rT3 to elevate and become an issue. It could be. But just based on the responses I have seen in the past few days, it has raised my suspicions as far as is anyone really paying attention? I just don't see it yet. People are dismissing the question or appealing to authority ("smart people say do it so just shut up..etc"). The question could easily be closed by a single reference to a single study where rT3 was taken into account and found to not be an issue.
Just thinking about it with a Grok hat on, one would think that even 24 hrs here and there would not send one's hormones into a permanent tailspin. But I'm just guessing. I just want to see some numbers, or know that people advocating this know enough to pay attention and get numbers. So far it does not seem to be the case.