Iodine and Hashimoto’s: Finding the Right Balance

Iodine is one of the most important minerals for thyroid health — and one of the most misunderstood. It is essential for producing thyroid hormones, and a deficiency can lead to hypothyroidism and goitre. But for people with Hashimoto’s thyroiditis, too much iodine can sometimes make symptoms worse and trigger an autoimmune flare. Understanding how iodine interacts with the immune system is critical if you have Hashimoto’s or other autoimmune thyroid conditions.

Why Iodine Matters for Thyroid Health

Your thyroid needs iodine to make thyroxine (T4) and triiodothyronine (T3). In countries where iodine deficiency is common, iodine supplementation has virtually eliminated goitre and hypothyroidism. However, in iodine-sufficient countries such as the UK, the US, and much of Europe, excess iodine intake can sometimes be a problem — particularly for those with Hashimoto’s.

Iodine and Hashimoto’s: The Research

Studies have shown that high iodine intake can:

• Increase thyroid antibody levels (anti-TPO and anti-Tg)

• Trigger autoimmune thyroiditis in genetically susceptible individuals

• Worsen hypothyroid symptoms in some people

On the other hand, too little iodine can cause its own issues, including low thyroid hormone production and fatigue. This is why a personalised approach is so important.

The Role of Selenium in Iodine Metabolism

Selenium is another key mineral that works hand-in-hand with iodine. Selenium helps neutralise oxidative stress created during thyroid hormone production. When selenium levels are low, excess iodine can become inflammatory and damage thyroid cells. Research suggests that selenium supplementation can lower thyroid antibody levels in people with Hashimoto’s, especially when iodine intake is moderate and not excessive.

--- Case Study: Iodine Contrast and a Severe Hashimoto’s Flare ---

Earlier this year, one of our clients with Hashimoto’s underwent a CT scan using iodine-based contrast dye. Within days, she developed a severe autoimmune flare: her thyroid became swollen and painful, her energy levels plummeted, and her brain fog intensified. Her antibody levels spiked significantly. After this event, even small amounts of iodine from iodised salt or seaweed triggered her symptoms again.

This case highlights how powerful iodine can be as an immune trigger for certain individuals. We worked with this client to remove unnecessary iodine from her diet, optimise her selenium and antioxidant status, support detoxification pathways, and calm her inflammation. Over time, she regained stability and learned how to manage future exposures.

Functional Medicine Approach to Iodine and Hashimoto’s

At The Autoimmune Clinic, we don’t take a one-size-fits-all approach to iodine.

Instead, we:

• Assess iodine status through dietary review and testing if appropriate.

• Check thyroid antibodies (anti-TPO, anti-Tg) and monitor changes over time.

• Support selenium and antioxidant pathways to protect thyroid tissue.

• Introduce or limit iodine gradually, watching for changes in symptoms.

• Address root causes of autoimmunity, including gut health, stress, blood sugar balance, and toxin exposure.

Practical Tips for Managing Iodine with Hashimoto’s

• Avoid high-dose iodine supplements unless recommended by a practitioner.

• Check your multivitamin — many contain iodine, which may or may not be appropriate for you.

• Include selenium-rich foods such as Brazil nuts, fish, and eggs, or supplement under guidance (typically 100–200 mcg/day).

• Be mindful of iodine-rich foods like seaweed and kelp. Include them in moderation and track symptoms.

• Inform your doctor before scans — if you have Hashimoto’s and need iodine-containing contrast dye, ask about monitoring and support before and after the procedure.

Key Takeaways

Iodine is essential for thyroid hormone production, but excess intake can worsen Hashimoto’s in some individuals. Selenium plays a protective role and should be optimised first to reduce oxidative stress and antibody activity. Ultimately, personalised testing and ongoing monitoring are key to finding the right balance and determining your unique iodine tolerance.

If you have Hashimoto’s and are unsure whether iodine is helping or hurting, we can help you take the guesswork out of your thyroid health.

Book a discovery call with The Autoimmune Clinic. Both Muriel and Claire are highly expeirenced practitioners supporting individuals with Hashimoto's. Together they will help you explore your triggers, calm your immune system, and create a clear plan for feeling better.

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