How Thyroid Health Affects The Immune System Renewed Vitality Oxyenergys L Carnitine. My go to pre post workout supplement. Pre workout I usually take it before my workout session for energy production. Post workout Ill take it the day after my workout Thyroid Supplement with L Carnitine for Cats Only Natural Pet Thyroid Supplement with L Carnitine for Cats Only Natural Pet AcetylLcarnitine suppresses thyroid hormoneinduced and spontaneous anuran tadpole tail shortening Hanada 2013 Hereditas Wiley Online Library Altered carnitine acylcarnitine profiles in levothyroxine treated congenital hypothyroid patients with fatigue: An LC MS MS based study from Bangladesh PLOS One