I found a study in Pigs demonstrating a positive effect of L-Carnosine on serum T3 levels.
"The results showed that there was a significant increase in serum T3 and T4 in pigs fed with 0.1% LC."
Effects of Dietary L-carnosine and Alpha-lipoic Acid on Growth Performance, Blood Thyroid Hormones and Lipid Profiles in Finishing Pigs
"The results showed that there was a significant increase in serum T3 and T4 in pigs fed with 0.1% LC."
Effects of Dietary L-carnosine and Alpha-lipoic Acid on Growth Performance, Blood Thyroid Hormones and Lipid Profiles in Finishing Pigs