The Iodine-Thyroid Connection

A woman's neck is examined by a doctor.

Iodine is essential for the proper functioning of the thyroid.

The thyroid, a small butterfly-shaped gland located in the neck, is important for regulating the body's metabolism, growth, development, and more. Iodine is essential for the proper functioning of the thyroid, so much so that iodine deficiency symptoms can sometimes mimic the symptoms of hypothyroidism and/or lead to outright hypothyroidism (1).


This blog post covers how iodine impacts thyroid function and the many areas of the body that may be compromised by suboptimal thyroid function.

The Role of Iodine in Thyroid Function & Hormone Production

Iodine is an essential trace element that the body cannot produce, making dietary intake critical. The thyroid gland absorbs iodine from the bloodstream and uses it to produce thyroid hormones thyroxine (T4) and triiodothyronine (T3) (2). These hormones regulate many body functions as described below.

The process is straightforward:

  1. Iodine Uptake: The thyroid gland captures iodine from the bloodstream.

  2. Hormone Production: Iodine is incorporated into the structure of T4 and T3.

  3. Hormone Release: These hormones are released into the bloodstream where they travel throughout the body to influence various areas.

A woman touches her neck. The outline of her thyroid gland is highlighted.

Key Functions of Thyroid Hormones

When considering the impact of iodine deficiency or insufficiency on thyroid function, it is important to understand the diverse roles that thyroid hormones play in our well-being. Here is a list of the key functions of thyroid hormones T3 & T4:

1. Regulate Metabolism (3)

2. Promote Healthy Growth and Development (4,5)

3. Maintain Heart Function - Especially Heart Rate & Blood Pressure (6)

4. Regulate Body Temperature via Heat Production in Cells (7)

5. Affect Digestion & Gastrointestinal Motility (8)

6. Influence Muscle Strength & Function (9)

7. Maintain Skin Hydration & Texture and Hair Growth & Quality (10)

8. Regulate Menstrual Cycle & Reproductive Health (11)

9. Support Nervous System Function - Particularly Reflexes & Cognitive Function (12)

10. Promote Protein Synthesis for Tissue Repair & Growth (13)

11. Regulate Cholesterol Levels & Other Blood Lipids (14)

12. Support Psychological Well-being, Mood, & Mental Health (12)

An understanding of the wide range of thyroid functions in the body helps to make it clear why low iodine, and by extension low thyroid, may include symptoms like weight gain, dry skin, fatigue, cold limbs, brain fog, low mood, constipation, and more. 

The thyroid gland on an X-ray.
A vial labeled "thyroid panel."

What To Do If you Suspect Iodine Deficiency?

The first step to take if you suspect that you aren’t consuming enough iodine is to assess your diet — a nutritionist can help with this. If your diet is low in iodine, you may wish to supplement with iodine-containing foods and/or iodine supplements. You may also wish to discuss a 24 hour urinary iodine concentration test with your healthcare provider.

How Much Iodine Is Safe To Supplement With?

When supplementing a healthy diet in adults and teens, the usual dose of iodine is usually 150 mcg per day, which is equal to one drop of our Liquid Iodine With Kelp. For children iodine needs are lower and therefore the usual dose is 1 drop daily or several times per week. Higher doses may be required to correct a deficiency. Most people notice a boost in energy when supplementing with iodine, particularly if they are deficient.


The tolerable upper limit for iodine is 200 mcg (age 1-3 years), 300 mcg (age 4-8 years), 600 mcg (age 9-13 years), and 900 mcg (age 14+). Excess iodine consumption may cause health issues. Always check with your healthcare provider before starting iodine supplementation for yourself or your children.

Summary

The iodine-thyroid connection underscores the importance of this essential nutrient — iodine — in maintaining thyroid health and overall well-being. By understanding the role of iodine and ensuring a balanced intake, we can support our thyroid function and prevent related health issues. Remember, both deficiency and excess of iodine can disrupt thyroid function, so finding the right balance through diet, lifestyle, and supplementation is important.

References:

  1. Zimmermann, M. B., & Boelaert, K. (2015). Iodine deficiency and thyroid disorders. The lancet. Diabetes & endocrinology, 3(4), 286–295. https://doi.org/10.1016/S2213-8587(14)70225-6

  2. Knezevic J, Starchl C, Tmava Berisha A, Amrein K. Thyroid-Gut-Axis: How Does the Microbiota Influence Thyroid Function? Nutrients. 2020 Jun 12;12(6):1769. doi: 10.3390/nu12061769. PMID: 32545596; PMCID: PMC7353203.

  3. Danforth, E., Jr, & Burger, A. (1984). The role of thyroid hormones in the control of energy expenditure. Clinics in endocrinology and metabolism, 13(3), 581–595. https://doi.org/10.1016/s0300-595x(84)80039-0

  4. Zhu, S., Pang, Y., Xu, J., Chen, X., Zhang, C., Wu, B., & Gao, J. (2022). Endocrine Regulation on Bone by Thyroid. Frontiers in endocrinology, 13, 873820. https://doi.org/10.3389/fendo.2022.873820

  5. Hanley, P., Lord, K., & Bauer, A. J. (2016). Thyroid Disorders in Children and Adolescents: A Review. JAMA pediatrics, 170(10), 1008–1019. https://doi.org/10.1001/jamapediatrics.2016.0486

  6. Klein, I., & Danzi, S. (2016). Thyroid Disease and the Heart. Current problems in cardiology, 41(2), 65–92. https://doi.org/10.1016/j.cpcardiol.2015.04.002

  7. Filfilan W. M. (2023). Thyroid Hormones Regulate the Thermoregulatory Mechanisms of the Body: Review. Pakistan journal of biological sciences : PJBS, 26(9), 453–457. https://doi.org/10.3923/pjbs.2023.453.457

  8. Xu, G. M., Hu, M. X., Li, S. Y., Ran, X., Zhang, H., & Ding, X. F. (2024). Thyroid disorders and gastrointestinal dysmotility: an old association. Frontiers in physiology, 15, 1389113. https://doi.org/10.3389/fphys.2024.1389113

  9. Di Iorio, A., Paganelli, R., Abate, M., Barassi, G., Ireland, A., Macchi, C., Molino-Lova, R., & Cecchi, F. (2021). Thyroid hormone signaling is associated with physical performance, muscle mass, and strength in a cohort of oldest-old: results from the Mugello study. GeroScience, 43(2), 1053–1064. https://doi.org/10.1007/s11357-020-00302-0

  10. Hussein, R. S., Atia, T., & Bin Dayel, S. (2023). Impact of Thyroid Dysfunction on Hair Disorders. Cureus, 15(8), e43266. https://doi.org/10.7759/cureus.43266

  11. Koutras D. A. (1997). Disturbances of menstruation in thyroid disease. Annals of the New York Academy of Sciences, 816, 280–284. https://doi.org/10.1111/j.1749-6632.1997.tb52152.x

  12. Sawicka-Gutaj, N., Zawalna, N., Gut, P., & Ruchała, M. (2022). Relationship between thyroid hormones and central nervous system metabolism in physiological and pathological conditions. Pharmacological reports : PR, 74(5), 847–858. https://doi.org/10.1007/s43440-022-00377-w

  13. Safer J. D. (2013). Thyroid hormone and wound healing. Journal of thyroid research, 2013, 124538. https://doi.org/10.1155/2013/124538

  14. Mullur, R., Liu, Y. Y., & Brent, G. A. (2014). Thyroid hormone regulation of metabolism. Physiological reviews, 94(2), 355–382. https://doi.org/10.1152/physrev.00030.2013

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