Effects of Lcarnitine on Thyroid Hormone Metabolism and on Physical Exercise Tolerance If you are like a lot of people, you may have never heard of carnitine but this important nutrient is critical for our body's ability to optimally burn fat required for energy. Frontiers Association between fatigue, peripheral serotonin, and L carnitine in hypothyroidism and in chronic fatigue syndrome Does Acetyl L Carnitine Help Depression? Thyroid Warning!