> ## Documentation Index
> Fetch the complete documentation index at: https://markers.iollo.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Thyroxine (T4) Free

Thyroxine (T4) Free is one of the main thyroid hormones and is important for regulating metabolism. High or low levels of T4 Free can indicate thyroid dysfunction.

## iollo markers that associate with Thyroxine (T4) Free

### Alanine

Thyroid hormones like T4 have significant effects on amino acid metabolism. Altered T4 levels may lead to changes in alanine and other amino acids.

<Accordion title="References">
  Larsen, P. R., & Kohn, L. D.. Thyroid Hormone Regulation of Metabolism - PMC - NCBI. *Endocrine Reviews* (2012). [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4044302/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4044302/)
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### Carnitine

Thyroid hormones regulate fatty acid oxidation. Carnitine is essential for fatty acid transport and metabolism, linking it indirectly to T4 status.

<Accordion title="References">
  Lombardi, M., Cuppari, L., & Muscatelli, R.. Thyroid hormone controls carnitine status through modifications of carnitine palmitoyltransferase activity. *Molecular and Cellular Endocrinology* (2002). [https://pubmed.ncbi.nlm.nih.gov/11964131//url](https://pubmed.ncbi.nlm.nih.gov/11964131//url)

  Lombardi, M., Cuppari, L., & Muscatelli, R.. Usefulness of l-Carnitine, A Naturally Occurring Peripheral Antagonist of Thyroid Hormone, in the Treatment of Hyperthyroidism. *Journal of Clinical Endocrinology and Metabolism* (1995). [https://academic.oup.com/jcem/article/86/8/3579/2848640/url](https://academic.oup.com/jcem/article/86/8/3579/2848640/url)
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### Phenylalanine

Phenylalanine is converted to tyrosine, which is then used to synthesize T4. Changes in phenylalanine availability can affect downstream T4 levels.

<Accordion title="References">
  Paloma Health. "Phenylalanine Benefits For Thyroid Health". *Paloma Health* (2022). [https://www.palomahealth.com/learn/phenylalanine-benefits-thyroid](https://www.palomahealth.com/learn/phenylalanine-benefits-thyroid)

  Garg, R.. "Effects of Dietary Phenylalanine and Tyrosine Supplements on ... - NCBI". *NCBI* (2022). [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8864120/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8864120/)

  Braverman, L. E., & Cooper, D. S.. "The many faces of thyroxine - PMC - NCBI". *NCBI* (2020). [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7242060/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7242060/)

  Schultz, J., et al.. "Alterations in the tyrosine and phenylalanine pathways revealed ... - Nature". *Nature* (2019). [https://www.nature.com/articles/s41598-019-40186-5](https://www.nature.com/articles/s41598-019-40186-5)
</Accordion>

### Taurine

Taurine plays a role in thyroid hormone metabolism and has been shown to modulate T4 levels in some studies.

<Accordion title="References">
  Kohrle J, Brabant G, Dixit K, Yap B, Strasburger CJ, Piehl S, Heberer T, Balizs G, Scanlan TS, Smits R, Koksch B, et al.. Metabolism of Thyroid Hormone - Endotext - NCBI Bookshelf. *NCBI Bookshelf* (2017). [https://www.ncbi.nlm.nih.gov/books/NBK285545/](https://www.ncbi.nlm.nih.gov/books/NBK285545/)

  Bianco AC, Gereben B, McAninch EA, Ribeiro MO. Thyroid hormone receptor α in skeletal muscle is essential for T3 actions promoting metabolic rate via coordinated regulation of fiber-type. *FASEB Journal* (2020). [https://faseb.onlinelibrary.wiley.com/doi/full/10.1096/fj.202001258RR](https://faseb.onlinelibrary.wiley.com/doi/full/10.1096/fj.202001258RR)

  Zhang L, Wang J, Zhang H, Wang J, Li L, Zhang L, Zhao J. Taurine dietary supplementation attenuates brain, thyroid, testicular disturbances and oxidative stress in streptozotocin-induced diabetes. *Journal of Functional Foods* (2017). [https://www.sciencedirect.com/science/article/pii/S2314853517300720](https://www.sciencedirect.com/science/article/pii/S2314853517300720)

  Zhang Y, Li L, Wang J, Zhang H, Li X, Zhang L. Effect of taurine on thyroid hormone and second messenger in rat heart after exhaustive exercise. *Journal of Applied Physiology* (2010). [https://pubmed.ncbi.nlm.nih.gov/21179805/](https://pubmed.ncbi.nlm.nih.gov/21179805/)
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### Tyrosine

Tyrosine is a precursor for the synthesis of thyroid hormones including thyroxine (T4). Alterations in tyrosine levels can directly impact T4 production.

<Accordion title="References">
  Cleveland Clinic. Thyroid Hormone: What It Is & Function - Cleveland Clinic. *Cleveland Clinic* (2022). [https://my.clevelandclinic.org/health/articles/22391-thyroid-hormone](https://my.clevelandclinic.org/health/articles/22391-thyroid-hormone)

  VA.gov. HYPOTHYROIDISM - VA.gov. *VA.gov* (2003). [https://www.va.gov/WHOLEHEALTHLIBRARY/docs/Hypothyroidism.pdf](https://www.va.gov/WHOLEHEALTHLIBRARY/docs/Hypothyroidism.pdf)

  StatPearls - NCBI Bookshelf. Physiology, Thyroid Hormone - StatPearls - NCBI Bookshelf. *StatPearls - NCBI Bookshelf* (2023). [https://www.ncbi.nlm.nih.gov/books/NBK500006/](https://www.ncbi.nlm.nih.gov/books/NBK500006/)
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