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Should Pregnant Women With Hashimoto’s Thyroiditis Take Iodine?

Most people reading this know that iodine is important for the formation of thyroid hormone.  There is a good amount of evidence that an iodine deficiency during pregnancy can lead to health issues with the developing fetus.  And so to reduce the chances of health issues developing in the fetus, it probably would make sense for all pregnant women to take a prenatal vitamin with iodine during pregnancy, or perhaps a separate iodine supplement in some cases.  But many women with Hashimoto’s Thyroiditis are told to completely avoid iodine.  And so what approach should pregnant women with Hashimoto’s Thyroiditis take?

While some healthcare professionals will recommend for everyone with an autoimmune thyroid condition to avoid iodine, I don’t necessarily share this viewpoint.  However, even though I feel that s0me people with thyroid and autoimmune thyroid conditions can benefit from iodine supplementation, I am very cautious when it comes to recommending iodine to people with Hashimoto’s Thyroiditis.  In some cases iodine can trigger an autoimmune response, and may worsen the condition of someone with Hashimoto’s Thyroiditis.  On the other hand, some people with Hashimoto’s Thyroiditis have benefited from supplementing with iodine.

Understanding The Importance Of Iodine To The Developing Fetus

Beginning in early gestation, maternal thyroid hormone production normally increases by 50%, and this requires an adequate iodine supply that is obtained primarily from the diet and/or as supplemental iodine (1) [1].  In addition, fetal thyroid hormone production increases during the second half of pregnancy, which further contributes to the increased requirements of maternal iodine due to the fact that iodide readily crosses the placenta (2) [2].  Because of increased thyroid hormone production, increased renal iodine losses, and fetal iodine requirements in pregnancy, dietary iodine requirements are higher in pregnant adults than in nonpregnant adults (2) [2].

Iodine deficiency isn’t something to take lightly, and numerous studies demonstrate the importance of iodine sufficiency during pregnancy.  One study provides evidence that even mild iodine deficiency during pregnancy can have long-term adverse impacts on fetal neurocognition that are not ameliorated by iodine sufficiency during childhood (3) [3].  In other words, any damage in fetal brain function due to an iodine deficiency supposedly isn’t reversible by correcting this deficiency during childhood.  Another study looked to assess whether a mild iodine deficiency during early pregnancy was associated with an adverse effect on child cognitive development (4) [4].  The results of the study showed the importance of adequate iodine status during early gestation and emphasize the risk that low iodine levels can pose to the developing infant, even if the iodine deficiency is mild.

Why Do Many People With Hashimoto’s Thyroiditis Avoid Iodine?

The big concern with iodine consumption in autoimmune thyroid conditions is that it might exacerbate the autoimmune response.  I actually wrote about this in a post entitled “Can Taking Iodine Cause An Autoimmune Thyroid Condition? [5]”  In the article I discussed how there is evidence that consuming iodine can increase the TPO antibodies.  However, I also mentioned how adequate selenium is important for the oxidation of iodide to iodine, and if someone has a selenium deficiency then this can cause oxidative damage.  As a result, taking selenium is important when supplementing with iodine.  Does this mean that people who take iodine and selenium won’t have any problems?  Not necessarily.  First of all, other vitamins and minerals are also important to supplement with, such as magnesium.  It’s also a good idea to supplement with vitamin C and the B vitamins.  But some people who do this still don’t do well when consuming iodine.

Plus, another factor to consider with Hashimoto’s Thyroiditis is that the increase in thyroid antibodies itself can pose a risk to the fetus…especially in the first trimester of pregnancy.  So if taking iodine happens to worsen the autoimmune response, then this might cause further harm to the baby.  On the other hand, sometimes the pregnancy itself will suppress the autoimmune component.  And if this is the case then this will greatly reduce the chances of iodine causing any problems. This once again is assuming the proper precautions are taken.

Should Pregnant Women With Hashimoto’s Thyroiditis Avoid Iodine?

This is an obvious dilemma for pregnant women who have Hashimoto’s Thyroiditis.  Should they avoid supplementation with any iodine and avoid all foods with iodine, and hope that the baby will be fine?  Or should they “take the chance” and take a prenatal vitamin with iodine, and hope that this doesn’t trigger an autoimmune response?  Of course another option is to have pregnant women test to see if they have sufficient levels of iodine.  This can be a catch-22, as myself and many other natural healthcare professionals recommend a 24-hour iodine loading test through the urine, which involves taking a 50 mg tablet of Iodoral before performing the test.

I’m in favor of a prenatal vitamin with iodine for women with Hashimoto’s Thyroiditis.  After all, in most cases we’re talking about 150 to 200 mcg of iodine, which is a fairly small dose.  Plus, taking iodine in the presence of these other nutrients will usually minimize any negative effects of the iodine.  While there are people who seem to have problems tolerating even small doses of iodine, remember that we’re talking about risks vs. benefits here, and in those women with Hashimoto’s Thyroiditis, it is my opinion that the risk of completing avoiding iodine during pregnancy is in most cases greater than the risks of having a small amount of iodine in the form of a prenatal vitamin.

Are there cases when a pregnant woman with Hashimoto’s Thyroiditis should consider taking a separate iodine supplement?  This of course is even more controversial.  The problem is that there aren’t any clinical trials which involves pregnant women taking higher doses of iodine.  And by higher doses I don’t necessarily mean 25 to 50 mg per day, but even 6 to 12 mg/day of iodine, which is well above the RDI.  However, I did come across a case study where three newborns developed congenital hypothyroidism, and it seems that excess maternal iodine ingestion was the cause (5) [6].  All three newborns had to go on levothyroxine, although 2 of the newborns were able to discontinue levothyroxine a few weeks after the excess maternal iodine ingestion was discovered.  And so in two of these newborns the hypothyroidism was transient, although one of the babies remained on levothyroxine at 30 months of age.

With that being said, I have worked with some pregnant women with autoimmune thyroid conditions who were taking higher doses of iodine on their own, and in none of these cases was there harm done to the baby.  To be fair, I’ve only had a few pregnant women take higher doses of iodine (all took it on their own), and so I’m not suggesting that taking higher doses of iodine during pregnancy is safe.  I personally don’t recommend for pregnant women to take very high doses of iodine, regardless of whether or not they have Hashimoto’s Thyroiditis.

In summary, there is a lot of evidence which demonstrates the importance of iodine sufficiency during pregnancy.  However, since many people with Hashimoto’s Thyroiditis try everything to avoid iodine then this brings up a dilemma.  Although I’m not suggesting that women with Hashimoto’s Thyroiditis should supplement with high doses of iodine, in most cases, taking a prenatal vitamin with iodine won’t exacerbate the autoimmune response, and at the same time will provide the developing fetus with a small amount of iodine that is necessary for proper cognitive development.