Ehm. Not really interesting for anyone not undergoing thyroid replacement therapy

Right, so, this is just to collect my thoughts and will be completely uninteresting for anyone but me (yes, I'm at work, but I can't focus on work beause my legs are spasming again making me panic about coming down with a spot of fibromyalgia/rheumatism/ALS)

Fact: a lot of people feel like crap when they start T4 hormone replacement therapy
(Me: muscle weakness, muscle spasms, joint pain, general feeling of being 'crummy', anxiety. Other common ones I've been spared: short term memory problems and migraine)

Supposed fact: you can't be allergic to Levothyroxine because it is an exact replica of the body's own hormone.
This is the cause of extremely heated debates bordering on hazing on hypothyroid forums: those that insist they feel bad because the hormone they are getting is synthetic and that the solution is natural thyroid hormone (ie Armour) vs those that claim that this is insane, they just need a higher dose.

Possible solution/exlanation:

Both could be right - Levothyroxine only supplies T4, which the body is supposed to turn into T3. However, not everyone's bodies have the same ability to turn T4 into T3 for various reasons, so in some people they get too much T4 and not enough T3. Since Armour includes actual T3, this can correct this problem. So, they are not really getting better because the drug is natural as opposed to synthetic, but rather as a side-effect of the drug being natural they get an extra hormone. In theory, this should mean that combined T3/T4 hormone replacement therapy could work just as well.

Caveat: natural thyroid hormone from pigs already has the right balance between T3 and T4, whereas getting that balance correct by supplying T3 and T4 seperately can be trickier, especially since T3 has a much shorter half-life. In addition, Armour also includes other hormones involved in thyroid function, and if you have an issue with producing any of these, Armour would help whereas T3/T4 combination wouldn't help.

Not helping discussion: argument about the fact that Armour is less standardized than synthroid drugs because levels of T3/T4 will vary (like the sweetness of strawberries depending on season). I have seen arguments both supporting and opposing this theory, I'm not convinced either way.

So, this part I get. The next possible explanation for feeling crummy when you start levothyroxine treatment, even if you maybe had no obvious symptoms before starting treatment, is apparently something called adrenal fatigue. Even subclinical adrenal fatigue, apparently to do with cortisone levels and extremely hard to measure, can cause worsening of hypothyroid symptoms when you first start medicating.
As far as I understand it, the symptoms will either get worse as you increase T4 levels to compensate for sudden, increased hypothyroid symptoms (despite normal TSH levels) until you feel like crap or sometimes, die, OR at some magical level the adrenal insufficiany will manage to correct itself using some substrate from the T4 and eventually if you keep elevating the dose you will be fine. Although first you will feel like crap for a really long time.

Yeah, that last one needs some more extensive research.