Frontiers Association between fatigue, peripheral serotonin, and L carnitine in hypothyroidism and in chronic fatigue syndrome Traditional Chinese Medicine for Hashimoto's Thyroiditis: Focus on Selenium and Antioxidant Phytochemicals The Benefits of Amino Acids for Hashimoto's Dr. Izabella Wentz, PharmD The most likely cause is Low Cortisol Explanation: 90% of all hypothyroid conditions are Hashimoto's. This is an autoimmune (your body attacks itself) condition. With this condition, the thyroid has antibodies that Association between fatigue, peripheral serotonin, and L carnitine in hypothyroidism and in chronic fatigue syndrome American ME and CFS Society