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ALA has only one study done on rodents that suggests it affects
conversion in tissues of T4 to T3. No human studies. Not all rodent
studies are applicable to humans. And the one study has not been
replicated.
This is the article those suggestions are based on 1991:
http://www.ncbi.nlm.nih.gov/pubmed/1815532
There are no other papers on this topic at PubMed more recently, and since ALA has been used for decades in Europe commonly, one would think something would have been published about it by now for humans.

It has been suggested that the mixed racemic R and S version which are not natural to the human body may be one reason.
When ALA is commercially manufactured, the S version appears and at first was not removed.

Today there are R only versions, and a new R that is water soluble and better absorbed... NaRALA.

Lipoic acid can however change your blood sugar, so people on medication may see a lowering effect and need medication adjustments.

I do not think the new R-lipoic stablized is going to do much at 100mg a day to the thyroid...and that is all you need because absorption is so much better. Many of us here use Doctor's Best brand.