The use of totally synthetic pain relievers should be banned in any amount.
With regards to from where the thyroid meds are obtained, are they really powdered pig thyroids? If that is the case, then I would see nothing wrong with eating thyroids, just as I see nothing wrong with eating liver.
As for concentrated forms thereof, that is interesting. It is well-known that many compounds and mixtures, both regulated and unregulated, are simply purified from natural sources, and thereby concentrated. I would submit that if the compound is a controlled substance such that it is either unlawful to possess or requires some sort of license to possess and distribute, and if circulating levels thereof can be significantly elevated by taking the purified form rather than the natural form, its use should be banned if that use is necessitated by training.
Same goes for iron, and other, supplementation. There would have to be a reliable and corroborated medical report that natural sources were tried before a purified source was permitted--and then it should be permitted only in those situations where its need was not necessitated by training.
The synthetic pain meds, forget about them. It's just another excuse to take something. You know what? I'm in pain today. I had a MASSIVE workout yesterday--my muscles are sore, I injured my rotator cuff, my left hand is sprained and all of my knuckles are bruised and swollen.
If I walked into a clinic as a normal individual and presented with these symptoms, I would be given pain relievers and likely local cortisone shots. But as an athlete? These are the sorts of conditions that produce training adaptations in response. That is the whole point of training, because next time I will be training with the aid of those adaptations, unless I go too hard too fast and exceed the pace of adaptation.
Any artificial means of increasing the body's natural pace of adaptation--whatever that is for any individual--should be disallowed, including Tylenol, Ibuprofen, whatever. For that matter, any artificial means of temporarily masking the symptoms of training-induced stimulus should be disallowed.
So, if thyroids meds are indeed "powdered pig thyroids", in the sense that they are entire thyroids that are dried and powdered, and the powder is then ingested, I don't see that as any different from eating whole, fresh or cooked thyroids. I would allow it. However, if there was any purification or concentration of the active ingredient, and that ingredient was a controlled substance, I would disallow it where its need was occasioned by training.
This thread continues to be a good read!