Iodine is one of those minerals that is very controversial and people tend to feel very strongly about one way or the other. There’s a lot of fear mongering, so I’m hoping I can clear up some of that noise for you today and share the facts along with my personal and clinical experience. One of the first things that comes to mind when I think of iodine is optimal thyroid health, which is crucial for fertility. Iodine is something we consider for all of our clients that want to conceive. Before we dig into all of the fun details of how iodine impacts fertility, I’m going to give you some background on iodine.
Iodine is a mineral that is specifically part of the halogen family, which includes chlorine, fluorine, and bromine. Halogens form a salt when they react with metals. Iodine is by far the most supportive halogen and is found in every cell of the body. Every gland concentrates iodine and uses it to create hormones. Iodine is essential for thyroid hormone production, and our thyroid contains the highest concentration of iodine in the body. All hormone receptors are dependent on iodine, which increases the sensitivity of the receptor to the hormone it is designed for. For example, iodine attaches to insulin receptors and improves glucose metabolism.
Iodine is also responsible for maintaining the health of our glands, specifically, our thyroid, ovaries, uterus, breast, and prostate. When an iodine deficiency is present, cystic/fluid-filled tissue can form and lead to a nodule and sometimes cancer. Dr. David Brownstein has been able to show that it generally takes 3-6 months of iodine supplementation to improve/reverse cysts, nodules, or disrupted glandular tissue. It can take years in severe cases, but this is pretty amazing. I have had husbands of clients with prostate enlargement and frequent urination (especially at night) that were able to reduce their prostate size and have huge relief using iodine. I’ve also seen iodine improve blood sugar levels and help people get off thyroid medication or lower their dose.
While iodine is essential for healthy hormones and glands, it’s also essential for our immune system. Poor immune system response is directly impaired by a sluggish thyroid. An iodine deficiency will lead to low thyroid hormone output and impact how our immune system functions. Iodine also has many therapeutic properties like being anti-bacterial, anti-viral, and anti-fungal.
Two forms of iodine are used in the body—iodine and then the reduced form of iodine, known as iodide. Iodide contains one extra electron and actually improves the solubility of iodine in supplements. Iodine is difficult to get into a solution that uses water as its solvent, but if you pair it with iodide, this fixes that problem. Different tissues in the body respond differently to different forms as well. For example, the thyroid gland and skin primarily use iodide, but breast and prostate tissue primarily use iodine.
We use iodine in order to make thyroid hormones. If you think about the two major thyroid hormones, T4 and T3, they are made of iodine molecules. T4 has four iodine molecules, while T3 has three iodine molecules. How does iodine get to that point? When we ingest iodine and iodide in the GI tract, it’s transported to our thyroid cells via iodine transport molecules, also known as NIS. When the brain senses that we need thyroid hormone, our hypothalamus gives our pituitary gland a little nudge to make thyroid stimulating hormone (TSH). That communicates to our thyroid that we need more thyroid hormone. Our thyroid then makes T4 (this is inactive thyroid hormone–think of it as a car in neutral) and then eventually T3 (this is active thyroid hormone–think of it as a car in drive).
TSH helps us make more NIS–those iodine transport molecules. When we don’t have enough iodine, we don’t make enough of those NIS molecules. The more iodine we have available, the more NIS we will make, and this allows us to utilize the iodine. This is why when we supplement with iodine, TSH levels go up. It’s making more of those NIS transporters to utilize iodine.
Iodine deficiency is a lot more common than you might think. 60% of women of reproductive age are deficient in iodine and iodine levels in the US alone have dropped by over 50% in the past 40 years, according to an NHANES study. Dr. David Brownstein, iodine expert, said that over 95% of his patients tested were deficient in iodine.
Why has iodine deficiency increased so much over the years, especially in the US? There are a few major reasons for this:
The last big issue is that the RDA is very low and does not help to reverse disease, only to prevent it.
What about iodized salt? Does this mean I should consume salt that contains iodine? Iodized salt actually isn’t a great source of iodine. Dr. David Brownstein cites an interesting study in his book, Iodine Why You Need It Why You Can’t Live Without It:
“In 1969, researchers looked at the bioavailability of iodine in salt versus bread. Two groups of people were studies; one group ingested a measured amount of iodine in salt, the other group ingested a measured amount of iodine in bread. Both subjected groups were estimated to ingest approximately 750mcg of iodine. By ingesting 750mcg of iodine, the expected serum levels of iodine would be 17.2mcg/L. However, the iodized salt group only had a serum level of 1.7mcg/L versus 18.7mcg in the bread group. This information would suggest the iodine in iodized salt is only 10% bioavailable.”
The other issue with refined salt is that it has had all of its minerals removed and has been exposed to toxic chemicals.
Any symptom that lines up with hypothyroidism will typically line up with iodine deficiency.
There are a few major areas to cover when it comes to iodine and how it impacts our fertility:
As you learned about earlier, adequate iodine is crucial for a well functioning thyroid and making plenty of thyroid hormone. A healthy thyroid is crucial for our ability to conceive and maintain a pregnancy. There are a few ways that a poorly functioning thyroid can contribute to difficulties with fertility and conception.
One eyeopening study shows how suboptimal thyroid health can impact fertility and conception here:
“A study showed that women who never achieved basal TSH <2.5 mIU/l or Thyrotropin releasing hormone-stimulated TSH <20 mIU/l had lower conception rates.[4] Women with TSH ≥2.5 mIU/l have significantly higher BMI, fasting insulin concentrations, total testosterone and free androgen indices and decreased sex hormone–binding globulin concentrations.”
Recurrent miscarriages and pregnancy complications have also been shown to be impacted by thyroid function:
“Pregnant women with subclinical hypothyroidism or thyroid antibodies have an increased risk of complications, especially pre-eclampsia, perinatal mortality, and miscarriage. Universal screening for thyroid hormone abnormalities is not routinely recommended at present, but thyroid function must be examined in female with fetal loss or menstrual disturbances. Practitioners providing health care for women should be alert to thyroid disorders as an underlying etiology for recurrent pregnancy loss.”
Thyroid health is essential for fertility, conception, and health during pregnancy and postpartum.
Our uterus actually takes up iodine and we even have iodine transporters in our endometrium. There’s even research that links a lack of iodine in the reproductive tissues to poor pregnancy outcomes. Iodine is required for optimal function of our reproductive organs and tissues. The next question would be what is keeping iodine from getting to these tissues? A big part of this is excess estrogen. Excess estrogen down regulates the sodium-iodide symporter than transports iodine. This can lead to less iodine in reproductive tissues as well as less iodine available for use in the body in general. Excess estrogen also leads to higher levels of thyroid binding globulin (TBG), which will bind to thyroid hormone and make it inactive.
In short, excess estrogen = less iodine = hypothyroid.
Iodine also has antibacterial properties and can be effective for those with endometritis that is preventing them from conceiving. Animal studies show that local iodine can decrease inflammation and improve conception rates. Pretty cool!
Did you know that our ovaries have the highest concentration of iodine outside of our thyroid gland? We store iodine in all tissues of the body but the amount varies. Why is this? Small and growing follicles take up iodine in order to develop properly. Iodine has also been found in follicular fluid. It makes sense that an iodine deficiency would be associated with reduced fertility. In an observational study conducted between 2005 and 2009 by the National Institute of Child and Human Development, 467 women trying to conceive were examined for iodine status. It was discovered that 44.3% were considered iodine deficient as determined by a urinary iodide concentration less than 50 mcg/g. Compared with women of normal urinary iodide concentration (>100 mcg/g), those with low iodine were 46% less likely to achieve pregnancy during each menstrual cycle. This is significant and something that we need more research on.
Unexplained infertility is defined as the lack of conception after one year of trying to conceive paired with the absence of a specific reason for infertility in either of the partners. Unexplained infertility is controversial since there are many cases of things like endometriosis, immune problems, deficiencies, etc. that are missed and could have been identified. This is likely why its prevalence ranges from 5-30% in different studies. Unexplained infertility is not a specific condition but rather the inability to conceive.
How does iodine deficiency impact those with unexplained infertility? Iodine deficiency is is known to lead to miscarriage, still births, and birth defects. In a review of iodine and fertility, the following statistics were shared:
‘More recently, Mills et al. (2018) conducted a study in over 500 women in the USA and found that those with lower urinary iodide levels had a 46% reduction in fertility. Moreover, women with low iodine levels also took longer to conceive, with 28% of the iodine deficient group failing to conceive at 12 months compared to only 12.5% in the iodine sufficient group. This suggests that iodine deficiency may contribute to a proportion of UI in developed countries.”
Do I think that iodine deficiency is the root cause of unexplained infertility for everyone? Definitely not, but I think it is an inexpensive area to investigate and treat for those that are struggling to conceive. This is why we always address this in our clients that want to conceive or have struggled in the past. If you’d like support on your fertility journey, you can learn more about our fertility group coaching program here.
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