one study i did find...
Effect of alpha lipoic acid on the peripheral conversion of thyroxine to triiodothyronine and on serum lipid-, protein- and glucose levels. Arzneimittelforschung. 1991 Dec;41(12):1294-8. Institute of Clinical Biochemistry, University of Bonn, Fed. Rep. of Germany.
The influence of alpha-lipoic acid on thyroid hormone metabolism and serum lipid-, protein- and glucose levels was investigated. In the first setup of experiments administration of alpha lipoic acid together with thyroxine (T4) for 9 days suppressed the T4 induced increase of T3 generation by 56%. This suppression was similar to that affected by 6-propylthiouracil (54%). Alpha lipoic acid or T4 alone did not affect the cholesterol level, but together they led to a reduction. alpha lipoic acid decreased the triglyceride level by 45%; the decrease induced by T4 or alpha lipoic acid plus T4 was not significant. Total protein and albumin levels decreased by alpha lipoic acid plus T4 treatment when compared to the alpha lipoic acid control. The slight increase in glucose level by alpha lipoic acid or T4 alone was not observed when they were administered together. In the second setup of experiments the administration of T4 for 22 days increased the serum T3 level 3-fold. When alpha lipoic acid was combined with T4 and the treatment continued, the T3 production decreased by 22%. T4 reduced cholesterol level by 30%, and alpha lipoic acid plus T4 further reduced it by 47%. The triglycerides were not affected. A moderate decrease in total protein was observed after treatment with T4 plus LA; T4 and alpha lipoic acid plus T4 decreased the albumin level. The decrease in serum glucose by T4 recovers by alpha lipoic acid treatment. These results demonstrate that alpha lipoic acid interferes with the production of T3 from T4 when it is co-administered with T4. The elevated level of T3, after T4 administration, is reduced by treatment with alpha lipoic acid.
it doesnt say when administered alone in patients with NORMAL functioning thyroid...