This can occur for a number of reasons, including taking in too little or too much iodine.
Excess iodine, however, can be particularly dangerous in these women.
The impact of too little iodine reaches further.

Illustration by Cindy Chung, Verywell
Mild iodine deficiency can also cause miscarriage.
The overall reduced use of table salt has been led by health concerns aboutsodium and high blood pressure.
As a result, only 53% of table salt sold in the United States is iodized.
If iodine deficiency isn’t the cause of hypothyroidism, then iodine supplements won’t be helpful.
This is especially true if you’re pregnant or planning to become pregnant.
This, though, is not without concern.
For some people with abnormal thyroid glands, excessive iodine can trigger or worsen hypothyroidism.
In addition, large amounts of iodine block the thyroid’s ability to make thyroid hormones.
While iodine poisoning is rare, the overconsumption of iodine can be just as problematic as consuming too little.
Are You Getting Enough or Too Much?
Rather, healthcare providers use thyroid tests to determine if your iodine intake is concerning or not.
The body does not make iodine, so it needs to come from dietary sources.
Iodine is found in animal protein, sea vegetables, iodized table salt, and fortified foods.
Yes, taking iodine supplements can worsen hypothyroidism.
High doses of iodine interfere with the production of thyroid hormones.
This can exacerbate problems for people with an already under-active thyroid.
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Yarrington C, Pearce EN.Iodine and pregnancy.J Thyroid Res.
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ThyroidCancer.com.Thyroid goiter: the diagnosis and treatment of thyroid goiters.