Iodine and Egg Quality: The Link You Might Not Know About

When we talk about nutrients that support fertility, iodine is rarely the first to come up. Most women are familiar with folate, vitamin D, omega-3s, and CoQ10 – but iodine? It’s typically dismissed as a “thyroid nutrient” and nothing more.

Yet emerging research is beginning to show that iodine’s influence goes far beyond thyroid hormone production. A new 2025 pilot study published in Scientific Reports has added important insight into its role in ovarian health, especially for women with diminished ovarian reserve (DOR) and low AMH - and the findings were remarkable.

A Closer Look at the Study

The pilot study investigated whether iodine supplementation could support egg development in women with diminished ovarian reserve – a group known to have fewer eggs and a higher proportion of lower-quality ones. These women completed two IVF cycles:

Cycle 1: No intervention

Cycle 2: After taking iodine (150 mcg/day) for two months

Researchers measured iodine status, egg development, and cellular changes within the ovarian environment. What they found suggests that iodine may play a much more direct role in fertility than previously understood.

Key results included:

✨ Iodine levels increased from borderline to optimal

Most participants started with iodine levels at the low end of normal – a common finding among women of reproductive age. After supplementation, these levels reached the optimal range associated with healthy thyroid and reproductive function.

✨ Mature egg count increased by nearly 70%

This is extraordinary for women with DOR, who typically struggle to produce mature, viable eggs. A higher mature egg count often translates to more embryos and improved IVF outcomes.

✨ Cell death in egg-supporting cells dropped from 64% to 23%

These are the granulosa cells that protect, nourish, and guide each developing egg. Reduced cell death indicates a healthier ovarian environment.

✨ Healthy cell growth tripled

Iodine appears to support more robust cellular activity, helping eggs develop within a more stable and protective environment.

In simple terms: iodine helped create conditions in the ovary that support better-quality eggs.

This wasn’t a large trial – which means we need bigger studies to confirm the results – but it adds to a growing body of evidence that iodine is essential not just for thyroid health, but for the reproductive system itself.

Why Iodine Matters for Fertility

We often underestimate iodine’s reach within the body. Beyond its central role in thyroid hormone production, iodine also contributes to:

1. Antioxidant and DNA-Repair Functions

The pilot study authors suggest that iodine’s antioxidant properties may help protect DNA during the egg maturation process. Eggs are vulnerable to oxidative stress, especially in women with DOR, advanced maternal age, autoimmune thyroid conditions, or chronic inflammation.

Iodine may help by:

• Reducing oxidative damage

• Supporting DNA repair pathways

• Protecting granulosa cells from premature cell death

This aligns with what fertility specialists already know: reducing oxidative stress is one of the most effective ways to improve egg quality.

2. Supporting Follicular Development

Ovarian cells, including granulosa cells, use iodine. It appears to influence how follicles grow, mature, and respond to hormonal signals. Healthy granulosa cells are critical, because they:

• Regulate estrogen production

• Provide nutrients to the egg

• Support final maturation before ovulation or retrieval

By improving granulosa cell survival and function, iodine may help create a more optimal environment for egg development.

3. Regulating Thyroid Hormones — Essential for Ovulation and Implantation

Even mild iodine deficiency can lead to subtle thyroid dysfunction, including slightly elevated TSH or low-normal T4 levels. For women with hypothyroidism, Hashimoto’s, or thyroid antibodies, this becomes even more important.

The thyroid-reproductive connection is well established. Thyroid hormones regulate:

• Follicle growth

• Ovulation timing

• Luteal phase integrity

• Progesterone signalling

• Early placental development

Low iodine → suboptimal thyroid function → disrupted ovulation + impaired egg quality.

This is why thyroid-related fertility challenges (including low AMH) often improve when nutritional gaps are addressed.

4. Supporting a Healthy Pregnancy

Once conception occurs, iodine continues to play essential roles:

• Fetal brain and nervous system development

• Healthy thyroid hormone production for mother and baby

• Reduced risk of miscarriage and preterm birth

• Improved cognitive outcomes in children

Requirements increase to 200–250 mcg/day in pregnancy, which is why consistent supplementation becomes so important.

Iodine Deficiency Is More Common Than We Think

Despite its importance, iodine deficiency is now widespread in the UK and many Western countries. Reasons include:

• Lower dairy consumption

• Soil depletion

• Eating mostly plant-based without seaweed or fish

• Higher needs during TTC, pregnancy and breastfeeding

For women on a fertility journey – especially those with low AMH, hypothyroidism, Hashimoto’s, or recurrent implantation failure – correcting iodine levels can be a meaningful part of the picture.

Where to Find Iodine

Food sources include:

• White fish (cod, haddock)

• Shellfish

• Seaweed (kelp, wakame, nori) — but be careful with excessive kelp

• Dairy

• Eggs

Most women trying to conceive will also benefit from a high-quality prenatal providing 150 mcg of iodine (the safe, evidence-based amount used in research and recommended by major health bodies).

This is why I ensure my clients always take a comprehensive prenatal that includes iodine, particularly if they have thyroid dysfunction, low AMH, or a history of poor egg quality.

The Takeaway

This small 2025 study doesn’t claim that iodine is a magic fix for low AMH or diminished ovarian reserve. But what it does show is powerful:

• When iodine levels move from borderline to optimal, the ovarian environment can change.

• Eggs mature more effectively.

• Cellular health improves.

• And the system becomes better equipped to support conception.

Sometimes, the quietest nutrients are the ones that make the biggest difference.

If you’d like help assessing your thyroid, nutrient status, or fertility supplements, consider 1:1 support and book in your initial call with me here - https://p.bttr.to/3sll0ms

Jen Xx