Thyroid stimulating hormone (TSH) is produced by the pituitary gland and regulates the production of thyroid hormones. High or low levels of TSH can indicate thyroid dysfunction.
Thyroid hormones increase carnitine excretion. Low thyroid function and high TSH may increase carnitine retention.
References
Salvatore Benvenga, Rosaria M. Ruggeri, Antonia Russo, Daniela Lapa, Alfredo Campenni, Francesco Trimarchi. Usefulness of l-Carnitine, A Naturally Occurring Peripheral Antagonist of Thyroid Hormone Action, in Iatrogenic Hyperthyroidism: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial. The Journal of Clinical Endocrinology & Metabolism (2001). https://doi.org/10.1210/jcem.86.8.7747M. A. R. D. Santos, M. A. R. Ferreira, C. A. R. Santos, et al.. Thyroid hormones and carnitine in the second trimester negatively affect fetal growth in the setting of severe early-onset intrauterine growth restriction. Frontiers in Endocrinology (2023). https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2023.1080969/fullSalvatore Benvenga, Rosaria M. Ruggeri, Antonia Russo, et al.. Thyroid hormones increase carnitine excretion: a true situation of secondary carnitine deficiency. The Journal of Clinical Endocrinology & Metabolism (2001). https://academic.oup.com/jcem/article/86/8/3579/2848640