Fascinating. At 100 mcg, I'd expect one to be able to tell the difference. This is especially surprising given the two groups. Namely, the symptomatic group and the healthy control group. I'd expect at least one group to be able to tell the difference. However, it's worth noting that the TSH between the two groups were virtually identical. The groups were selected based on hypothyroid symptoms rather than actual thyroid status.

The fact that healthy controls could not tell the difference is odd. It is both not what I expected and cuts against what the related lesswrong article says about discernibility to healthy subjects (odd given that lesswrong mentions this specific study). What may be happening is that the question was not specific enough. If subjects interpreted reduced vitality as a sign that they were not receiving thyroxine, then many might get is wrong. I wish they has a more thorough questionnaire on perception of drug effects. Even an informal "describe the experience" question would be nice.

All in all, I find it unlikely that this is accurate. There are at least two possibilities. It could indicate that the dose was not high enough, in which case the study is not testing what it thinks it's testing. That is supported the the fact that the TSH of the thyroxine group is barely out of the normal range. The other option, as mentioned above, is that they are not asking the right questions. If that is the case, that also seems to invalidate the findings.

In conclusion, this result means that we can't trust the study. I'm certain higher doses would be discernable from placebo to subjects. It is likely that it was discernible at this dose (100 mcg) if the right questions were asked. I'm thankful they included this outcome.

P.S. I found this study completely by accident, then found out it was related to that lesswrong article that I've always appreciated.

This is very interesting to note. This is some of the most direct evidence that hyperthyroidism shares some symptoms with hypothyroidism. I'd still like to know if liothyronine (T3) would show the same results. I suspect T3 would be better, especially given that it may be less likely to disturb sleep (because of the half life).

Graves disease has a average free T3 at least 3 times the upper normal range. This implies that there is only a little bit of wiggle room between high thyroid status and thyrotoxicosis. However, free T4 is at about twice as high as upper normal, so the total thyroid activity may be closer to 3.5 or 4 times the upper normal (assuming that T4 is roughly 10 times less potent than T3)

Most thyroiditis patients had total T3 in the upper reference range. Free T4, on the other hand, was nearly all above reference range. Graves' disease had half somewhat elevated and half extremely elevated levels for bot total T3 and free T4. I now just need data on free T3 (which in my recollection would be expected to scale tightly with total T3, so I may be able to predict the values).