Iodine and Hashimoto’s, Fertility and Pregnancy Doses: What You Need to Know.

Iodine—it’s the most controversial of nutrients when it relates to thyroid function and Hashimoto’s disease. On the one hand, we know that iodine deficiency leads to epidemics of goitre in areas where the nutrient is not available, but alternatively, the taking of iodine may have some risks if not implemented in the most optimal way.

In short, it is important to ensure that iodine is sufficient in the diet to ensure that the thyroid function is optimal in pregnancy, and iodine intake should also be adjusted to each patient’s individual situation; more information about that will be discussed below. This article will detail the role of iodine for Hashimoto’s and Hypothyroid patients in the particular times of preconception or pregnancy. This may differ from the role of iodine in a non-childbearing stage of life.

Iodine Deficiency

Iodine deficiency, which used to mainly be restricted to parts of the world where iodine was depleted in the local soil, has more recently been affecting industrialized nations as well. It is estimated that more than 800 million people are deficient in iodine worldwide, and this may be related in part to industrialized nations getting a large part of their food supply from non-local sources. Foods rich in iodine include seafood, milk and eggs; overall, vegans are more at risk for iodine deficiency. Food sources of iodine may vary, depending on the mineral content of the soil and food supply..

Iodine deficiency in the developed world may also be induced by bromide intake: Bromide is a halide element that is present in high amounts in pesticides, medications, and fire-retardant chemicals. Bromide competes with the same receptors that are used in the thyroid gland to hold iodine, thus increasing the deficiency. Urine tests are available which can determine iodine levels in the body, and whether or not bromides are displacing the uptake of iodine in the thyroid.

Iodine Deficiency: In the Times of Fertility and Pregnancy

Iodine deficiency causes hypothyroidism which has a major impact on fertility and can increase the risk of miscarriage. Even a mild deficiency during pregnancy can result in abnormal nervous system and endocrine development in babies. In cases where iodine deficiency is significant, babies can develop cretinism, as well as severe and permanent alterations in mental and physical development. Iodine deficiency is also particularly concerning in children, where it can cause abnormal development, and cognitive impairment. It has been estimated that iodine deficiency causes an average drop of 12 IQ points in children.

That said, it is also important to note that the intake of excessive amounts of iodine in pregnancy (2-3 grams daily) has been associated with severe hypothyroidism in the mother and transient suppression of the thyroid gland in the newborn baby. As a result, the amount of iodine intake in pregnancy should be at an optimal level.

When it comes to hypothyroidism, it is crucial to consider micronutrient deficiencies of selenium, as well as zinc and vitamin D, as these nutrients are critical for normal and healthy function of the thyroid gland.

It is beyond the scope of this article to go into detail on these nutrients, but I will say that zinc is needed to stimulate the pituitary gland into producing thyroid hormone, and also for the conversion of T4 to T3. Vitamin D is needed for cell receptivity to thyroid hormone, and  it also lowers autoimmune responses by improving the deficient T regulatory cell levels that are often present in Hashimoto’s thyroiditis.

Selenium is important for the conversion of T4 to T3, though large quantities of selenium are not needed for this function. Much of selenium’s benefit for the thyroid, however, comes from the immune system in that it regulates the production of reactive oxygen species and their metabolites. In patients with Hashimoto’s disease, and in pregnant women with anti-TPO antibodies, selenium supplementation decreases anti-thyroid antibody levels and improves the ultrasound structure of the thyroid gland.

Iodine and Hashimoto’s: Autoimmunity

In autoimmune conditions such as Hashimoto’s, where the immune system attacks the thyroid gland, iodine may cause a dangerous aggravation of the process. In such cases, when there is no iodine deficiency, sudden increases in iodine intake (especially in milligram amounts) should be avoided, and foods rich in iodine should be taken in moderation. In Grave’s disease (an autoimmune disease which causes the thyroid to become overactive), supplementation of iodine can cause an even more serious condition known as thyroid storm, which should be avoided at all costs.

It’s important to note that in patients who have Hashimoto’s disease, iodine deficiency can still pose a real concern to healthy thyroid function.

As such, we want to ensure that there is just the right amount of iodine for fertility or pregnancy patients with Hashimoto’s disease. In cases of autoimmune thyroid disease, it is recommended to test iodine levels through a urinary iodine test, or a dried urine iodine (which is far more convenient). If deficiency is established, small doses of iodine, along with appropriate amount of selenium may be administered to Hashimoto’s patients while monitoring labs and symptoms. Increasing amounts of iodine can then be administered gradually to replenish deficiency, always watching lab values to ensure that there is no aggravation.

Interestingly, it also appears that the negative effects of supplementation of iodine on Hashimoto’s disease may be related to selenium deficiency.

So, when using even small doses of iodine in patients with Hashimoto’s thyroiditis, it is important to ensure that selenium supplementation is at an optimal dosage.  Selenium reduces the damage that the autoimmune process does to the thyroid gland by quenching reactive oxygen species and by lowering thyroid antibodies.  

It’s important to note as well, that this article is focused around the topic of iodine and Hashimoto’s in fertility and pregnancy, and not about the use of iodine in hypothyroidism or Hashimoto’s disease in general. In my opinion, these two situations are entirely different. We must proceed with more caution with iodine in a fertility/pregnancy patient than in a hypothyroidism or Hashimoto’s patient who is not pregnant. Avoiding aggravation of autoimmunity is crucial, as it could impact the baby’s development.

  • For pregnant women – 300 micrograms per day
  • For women over 19 years of age – 220 micrograms per day.

These are the absolute minimums, and are most likely grossly underestimated, as we know that many women who have hypothyroid symptoms and labs do improve with higher dosages than this.

The World Health Organization says that the maximum tolerable intake for iodine is 1100mcg per day for adult and pregnant women—this amount is completely safe and is not associated with any increased risks. Significantly higher dosages are often used by complementary medicine practitioners with great benefit, however, if the patient is carefully investigated and does not have risk factors.

In general, higher doses of iodine should not be attempted without practitioner guidance, as the intake of higher levels may have some serious consequences.

Risks of Too Much Iodine

In many cases, higher amounts of iodine can be used safely if risk factors are considered, but using it in higher doses does carry some risk. These risks can seem very contradictory, but I do hope that the explanations below will be helpful.

Here are some of the risks of taking higher doses of iodine are (and again, these do not happen in most cases):

  1. Iodine-induced hyperthyroidism. In patients who are already iodine deficient, there is a risk of inducing hyperthyroidism when giving larger clinical doses of the nutrient. In some cases, this can actually be dangerous as it can cause cardiac dysfunction, including arrythmia.  This happens because thyroid nodules and thyroid cells (thyrocytes) can form in increasing numbers in the presence of iodine deficiency. Once these cells are re-exposed to significant amounts of iodine, they begin to produce large amounts of thyroid hormone, causing hyperthyroid symptoms.
  2. Iodine-induced hypothyroidism. In patients who are hypothyroid, or subclinical hypothyroid, the intake of larger amounts of iodine may cause what is known as the Wolf-Chaikoff effect. This effect is a transient condition of hypothyroidism after the intake of this nutrient. Iodine itself is a goitrogen, and can lower thyroid function when taken in high amounts. In the majority of cases, this resolves in 48 hours, but can persist in some instances.  This is prevalent in patients who have pre-existing hypothyroidism.
  3. Thyrotoxicosis and Autoimmune Thyroiditis such as Hashimoto’s disease. In some patients with Hashimoto’s or other autoimmune thyroid diseases, high doses of iodine may aggravate and trigger the autoimmune process and worsen the condition, leading to hypothyroidism over time.  Again, this is likely to occur in the presence of selenium deficiency. So if you have high TPO antibodies, it is important to supplement selenium when replenishing iodine deficiency. 


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