What Causes Thyroid Nodules? Exploring Iodine’s Impact on Thyroid Health

What causes thyroid nodules? You may be surprised to hear that thyroid nodules are actually quite common, with an estimated 50% of Americans developing nodules by the age of 60. While most thyroid nodules are harmless, they do raise questions about underlying thyroid health. 

In this article we’ll discuss what thyroid nodules are, the symptoms to look out for, and the essential role of iodine in thyroid function. Let’s also explore how iodine imbalances could be at the root of thyroid nodules, and why a root-cause approach matters for long-term healing.

LEFT: A healthy thyroid gland. RIGHT: Thyroid gland with multiple nodules. From Cleveland Clinic

What Are Thyroid Nodules?

Thyroid nodules are small lumps that form within the thyroid gland. The thyroid is a butterfly-shaped gland situated at the base of the neck that is essential for regulating metabolism, energy, and hormone levels. 

90-95% of nodules, whether a buildup of thyroid cells or fluid-filled cysts, are benign (non-cancerous) and never cause problems. However, some can be malignant, so ensure you discuss with your doctor if you feel anything abnormal on or around your thyroid gland. Nodules become increasingly more common with age and are more frequently seen among women.

Thyroid nodules are often discovered incidentally during routine physical exams, especially if someone is asymptomatic. However, symptoms can arise when nodules are large enough to compress their surroundings, possibly leading to swallowing difficulties, neck pressure, or a hoarse voice. 

They can also impact thyroid hormone production, causing either slow (hypothyroidism) or overactive (hyperthyroidism) thyroid function. This may result in fatigue, weight changes, constipation, mood shifts, or irregular menstrual cycles. Thyroid nodules may even coexist with autoimmune thyroid conditions such as Hashimoto’s thyroiditis or Graves disease. Regardless of one’s symptoms, nodules can be a sign of stress on the thyroid and a major reason to take a deeper look into thyroid health. 

Thyroid nodules can arise for several reasons. While iodine deficiency is a key factor that we’ll cover in the next section, other potential causes include chronic thyroid inflammation and genetics. In fact, having a family history of thyroid cancer may increase your risk of developing thyroid nodules.

Iodine’s Role in Thyroid Health

Iodine is an essential mineral that serves as the raw material for thyroid hormone production. Each individual thyroid hormone contains iodine. In fact, thyroid hormones are named according to how many iodine atoms they contain: inactive T4 (thyroxine) has 4 iodine atoms; active T3 (triiodothyronine) has 3 iodine atoms. Without sufficient iodine, the thyroid gland cannot produce enough hormones to keep metabolism and cellular energy stable.

Without enough iodine, the thyroid gland overcompensates by enlarging thyroid tissues in an attempt to collect more iodine. This can lead to thyroid nodules or goiter, an enlarged thyroid. While we certainly want adequate iodine to produce thyroid hormones, too much iodine can pose its own problems. Because of this, we consider iodine to be a “goldilocks” mineral, where we don’t want too little or too much, but rather just enough for optimal thyroid function. 

Key Considerations Before Supplementing With Iodine

While iodine is vital, jumping straight into supplementation without appropriate preparation can backfire. Thyroid nodules and thyroid dysfunction in general are often tied to chronic inflammation and oxidative stress. Adding iodine into an already inflamed environment may actually worsen oxidative damage if antioxidant defenses are not supported first and foremost.

You may be wondering if supplementation is even necessary in the first place. Historically, iodine fortification in salt (iodized salt) was designed to reduce deficiency worldwide. However, many individuals have moved away from using iodized salt, don’t consume many natural sources of iodine, and suffer the consequences of iodine insufficiency.

So where should you start? It’s imperative to take a functional nutrition approach, to calm inflammation and support antioxidant levels before replenishing iodine stores. We take you through this step-by-step in our Functional Thyroid Foundations group program – keep reading to learn more! Only once this foundation is established – inflammation reduced, oxidative stress addressed, and nutrient cofactors boosted – should iodine supplementation be considered.

Before supplementing, it’s important to understand the Wolff–Chaikoff effect, essentially what will happen in the initial adjustment period when iodine is introduced. This is when the thyroid temporarily suppresses hormone production in response to excess iodine. Thyroid-stimulating hormone (TSH) rises during this adjustment period. This is a normal and temporary response as the thyroid gland effectively “resets”, so avoid testing TSH levels within the first three months of iodine supplementation. 

It’s worth noting that not everyone adapts smoothly, and in some cases the thyroid stays within the Wolff–Chaikoff effect, leading to persistent thyroid hormone suppression. This is more likely to occur in children and individuals with high baseline thyroid inflammation, such as those with autoimmune Hashimoto’s, postpartum women who are already nutrient-depleted, or in immunocompromised individuals. For these groups, personalized guidance and monitoring is essential.

A Root-Cause Approach to Thyroid Nodules

Iodine plays a vital role in thyroid health and in preventing thyroid nodules, but it must be introduced with care. Supplementation should never be the first step. Instead, the priority is reducing inflammation and oxidative stress through a nutrient-dense diet, supportive antioxidants, and lifestyle practices that calm the immune system.

Our Functional Thyroid Foundations group program provides a clear 4-week roadmap for this process, offering delicious antioxidant-rich recipes, targeted supplement guidance, and practical strategies to lower oxidative stress, improve blood sugar balance, and support energy levels.

Thyroid nodules are rarely an isolated issue, and they usually reflect deeper thyroid dysfunction. By strengthening nutrition and lifestyle foundations first, you create the right environment for iodine to be used effectively, helping to manage nodules and support optimal thyroid function.

Written by Romana Brennan, MS, RDN