Miscarriages are incredibly common and occur in 10-20% of known pregnancies. This is the most common fertility concern that we help women overcome. The typical story we hear from clients that have gone through one or multiple miscarriages is that their provider explains it’s likely a chromosomal issue and no further action needs to be taken. Not surprisingly, we don’t love this answer. Could it be a chromosomal issue? Yes and that means you could consider focusing on egg and sperm quality as well as looking at stress and your environment. It doesn’t mean you do nothing. Could it be something else? Also yes and that’s where this newsletter comes in!
One of the first things that comes to mind when a woman shares that she has had a miscarriage is thyroid health. We always look at thyroid function when this is the case, even if a woman has been told their labs are “normal.” Why? Because subclinical hypothyroidism is very common and can pay a role in pregnancy complications including miscarriage. Just because your thyroid labs are within the normal range, doesn’t necessarily mean your thyroid is functioning optimally. This article is a great resource for learning more about how critical thyroid function is for fertility. One especially important excerpt is below:
“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.”
There are a few ways that a poorly functioning thyroid can contribute to difficulties with fertility and conception.
Hyperthyroidism can also lead to miscarriage because of how it can impact blood clotting factors.
Low levels of iodine can lead to low levels of thyroid hormone and increase our risk of miscarriage. 36% of women of childbearing age in the U.S. are deficient in iodine. That’s significant and something that is not discussed when it comes to the increasing rates of hypo and hyperthyroidism. Yes, iodine deficiency can also contribute to hyperthyroidism.
It’s not just our thyroid that iodine impacts though. 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!
Our uterus actually takes up iodine and we even have iodine transporters in our endometrium. There’s also 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!
We utilize iodine supplementation with many (not all–it’s not appropriate for everyone) of our fertility clients and find it to be very helpful and supportive for those with a thyroid health concerns and a history of miscarriage. Many of them of our clients have tried taking thyroid medication but didn’t notice a difference and were not able to maintain a pregnancy regardless of taking medication. That’s when iodine can be especially helpful and we see a lot of success.
There’s a lot more to miscarriage than thyroid function. We will eventually touch on all of these in the future, but for now, here is a list of areas to consider exploring:
If you have not listened to our free fertility foundations audio series, we cover a lot of these there as well! You can listen here
Want to learn more about your thyroid? Here is a great mini thyroid course that will help you dig deeper.
reminder: i’m currently accepting people into my Nurture Your Fertility program. you can learn more here about the program and fill out an application!
