Effects of L-carnitine on thyroid hormone metabolism and on physical exercise tolerance.
L-carnitine (CARN) is a water-soluble, naturally occurring quaternary amine ubiquitous in biological fluids and animal tissues; in these tissues, CARN plays an important role in energy metabolism. Skeletal muscles store about 95 % of a total of 20 g CARN contained in the adult human body, but high-intensity physical exercise decreases the CARN muscle content. The daily allowance of CARN is mainly satisfied by diet. Keeping in mind important interstudy differences, the general conclusion is that CARN supplementation may enhance athletic performance when coupled to physical exercise itself. Healthy, essentially sedentary persons and untrained individuals do not benefit from supplementation, and certainly not if CARN is administered for a few days. CARN was also shown to modulate thyroid hormone action in peripheral tissues, the most frequent modulation observed being inhibition.
Benvenga
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Sezione di Endocrinologia del Dipartimento Clinico Sperimentale di Medicina e Farmacologia, University of Messina School of Medicine, 98125 Messina, Italy. s.benvenga@me.nettuno.it
D000818:Animals; D002331:Carnitine / Q000008:administration & dosage / Q000378:metabolism*; D019587:Dietary Supplements; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D017079:Exercise Tolerance / Q000502:physiology*; D006801:Humans; D018482:Muscle, Skeletal / Q000378:metabolism*; D013963:Thyroid Hormones / Q000378:metabolism*
D013963:Thyroid Hormones; D002331:Carnitine