Doctor endocrinologist checking tyroide goiter of pregnant woman and holding hands on her throat, sluggish thyroid

Americans undergo an enormous number of scans each year. It is estimated that over 80 million CT scans are performed annually. That doesn’t include other scans such as coronary angiography, arthrography or myelography. It is not uncommon for a physician to order contrast media be injected during the X-ray exposure to enhance the clarity of the images and help with the diagnosis. There is, however, a downside to using contrast containing iodine for scans. A big dose of iodine can trigger HYPERthyroidism or HYPOthyroidism. In other words, contrast material used in CT scans and X-ray images can knock your thyroid out of whack as this reader reports.

Hyperthyroidism After Iodine:

Q. I injured my shoulder and two months later I had an arthrogram with iodine dye. Now I have heart palpitations, anxiety, dizziness and adrenaline rushes from hyperthyroidism.

I have seen an endocrinologist for the hyperthyroidism. She said I’ll need to wait six months after the arthrogram to be tested for excess thyroid. If my blood test doesn’t normalize, I may need to take methimazole. This drug can have serious side effects. Am I right that the iodine dye is probably to blame for my hyperthyroidism?

A. Diagnostic imaging such as CT scans or arthrography with iodine contrast media can trigger hyperthyroidism (Journal of Clinical Endocrinology and Metabolism, Feb. 2015).  Many health professionals are unaware of this complication. If they have heard of it at all, the assumption has been that it is extremely rare.

An Unappreciated Risk of Iodine for Scans:

When iodine is injected during a scan or during angiography the material is referred to as iodinated contrast media (ICM). To give you some idea of the dose involved we need to consider the recommended daily intake of iodine. It is 150 micrograms. That’s not much. It’s less than 1/5 of a milligram.

Now consider the dose of a typical ICM injection during a CT scan. Some experts estimate that it ranges from “2,500 to 5,000 micrograms of bioavailable free iodine and 15 to 37 grams of total iodine” (Journal of Clinical Endocrinology and Metabolism, Feb. 2015).

Another group of researchers described the ICM dose this way (Archives of Internal Medicine, Jan. 23, 2012).

“A typical dose of ICM contains approximately 13,500 micrograms of free iodide and 15 to 60 grams of bound iodine that may be liberated as free iodide in the body. This represents an acute idodide load of 90 to several hundred thousand times the recommended daily intake of 150 micrograms. Sudden exposure to high iodide loads, given in other contexts, can disrupt thyroid hormone regulations, resulting in hypothyroidism (Wolff-Chaikoff effect) or hyperthyroidism (Jod-Basedow).”

Symptoms of Hyperthyroidism:

Imagine drinking 5 cups of coffee all at once. Your metabolism would rev up. Some people describe hyperthyroidism as something akin to having their internal motor going way too fast.

  • Weight loss even after eating normally
  • Rapid pulse, sometimes exceeding 100 bpm without exercising; heart palpitations
  • Frequent bowel movements
  • Hand tremor
  • Feelings of being wired or overly caffeinated
  • Alterations in energy from fatigue to exhaustion
  • Hives or itching
  • Changes in vision, bulging eyes
  • Anxiety; difficulty sleeping
  • Cognitive impairment; confusion, scrambled brain effect

The Diagnostic Dilemma:

When physicians determine that people need CTs with contrast, that usually means iodine will be injected. It is relatively inexpensive and quite effective.

If a patient starts losing weight, feeling jittery or going to the bathroom four or five times a day, it may be linked to the iodine used in the scan or the coronary angiography. And if a person starts suffering symptoms of hypothyroidism several weeks after a scan, that too may be connected to the diagnostic procedure.

However, very few people who undergo a scan will be tested for hyper or hypothyroidism over the next few months. It takes a pretty good medical sleuth to figure this out. The effects of the excess iodine can last for several months or even a year or two. Some people may never return to normal thyroid function without medical treatment.

What to Do for Hyperthyroidism?

Your endocrinologist will need to track your thyroid function very carefully. She may need to prescribe a beta blocker to control your heart palpitations and adrenaline rushes until the iodine effect begins to wear off. You may also need to take an anti-thyroid medication such as methimazole if your thyroid gland does not calm down on its own. A low dose might not be as scary as it seems if you are monitored carefully.

Methimazole Side Effects:

  • Skin rash and/or itching
  • Digestive distress (nausea, indigestion, vomiting, changes in taste)
  • Joint pain, arthritis, muscle pain
  • Headache
  • Hair loss
  • Drowsiness, dizziness
  • Blood disorders, liver toxicity, kidney damage

The People’s Pharmacy Perspective:

Physicians who order iodine for scans need to be vigilant. Older people are especially vulnerable to hyper and hypothyroidism after such iodine exposure. Younger patients are not immune to this reaction, either.

Anyone who undergoes a scan with contrast should be advised to look out for signs of thyroid dysfunction. If symptoms occur, it is imperative that thyroid tests be performed promptly and appropriate treatment initiated until the thyroid gland recovers from the excess exposure to iodine.

Have you experienced symptoms after a scan with contrast? Please share your story in the comment section below.

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  1. Jo
    Midland Texas

    How would covering thyroid gland with shield prevent Hashimoto disease? That would not prevent the dye from affecting the thyroid.

    • Katie Cather
      Loomis, CA

      My thoughts exactly. It’s not the scan process, it’s the injected iodine.

  2. Sharon F

    Very interesting. I was diagnosed at 16 with HYPERthyroidism. Underwent radioactive iodine/lazer procedure and immediately became HYPOthyroid. As I am older, can never get a doctor to adjust meds to make me feel normal. As long as my T3 tests are normal they say I’m good. Sounds like I need a specialist. Thanks for an enlighting article and feedback!

  3. john h

    john h had test o n the 13 of Nov iodine contrast ct scan and 450 ml of barium taken twice pm on the 12th and 1 hour before my 7:45 test time for ultra sound , followed by ct scan . this was given to measure my aorta [aneurysm abdominal aortic without rupture ] . in creased B M s 3 -6 a day for 14 days dark urine increased urination felt poorly after test on the 3rd day 2-4am felt rotten close to passing out slowly came out “it “on the 14th night late pm had another weakened state and did pass out , came to on the floor by kitchen sink [ injured left knee] had to pull myself up and get to the toilet quick , the last of the diarrhea G I track is now back to normal … was all this getting rid of metals and iodine ?

  4. LI

    Then there’s the risk of an allergic or sensitivity reaction. I received contrast dye for a CT scan, and wound up in the emergency room. I was given a massive dose of steroids to stop the ever-increasing reaction. With several more days of steroids and Benadryl, the reaction finally subsided. My GP told me that I had a threshold reaction, in that it was the large dose of iodine in the contrast dye that triggered it. I can eat shrimp, with much lower amounts of iodine, without any trouble. So my reaction was not a true allergic reaction, as, in that case, any amount of the substance would have triggered it.

    My point here is to be careful. Just because one can eat shrimp with no problems doesn’t mean one won’t react to the iodine in contrast dye. The amounts of iodine are not comparable.

  5. Joan

    I am shocked that so many people were exposed to such a high dose of Iodine I get regular CT scans due to cancer but it is not Iodine they use because I knew about this problem and checked before my first one as I would have refused it as far as I know Lithium is the only drug that will bring the thyroid back to normal when caused by Iodine but needs to be given fairly quickly not weeks later I am glad you have highlighted this serious problem and I suggest everyone post it on social media

  6. Sally

    My Mom had a CT with contrast done to diagnose what was wrong with her. Turned out to be an very advance infection. She was admitted to the hospital right away. It was taking awhile to find a medicine that would work on the infection. She was very sick and in the middle of all this her kidneys starting shutting down due to the contrast used in the CT. She had to have dialysis done right in her hospital room for a few days. That was more than three years ago and she still has to be careful as not to damage the kidney anymore than it is.

  7. Lorna

    Now it makes since how I developed Hyperthyroidism at age 18. Within months of having an ICM procedure go bad, in which a nurse did not properly insert a catheter tube and dye spilled all over then had to repeat procedure, I started having atrial fibrillation, anxiety attacks, etc. Eventually symptoms were so bad with thyroid going both hypo then hyper the Drs couldn’t regulate it. So my thyroid had to be removed. If I had been told of the possible repercussion of this test, which wasn’t all that necessary, I would not have done it.

  8. Lori

    3 years ago I had several scans for diverticulitis with iodine and developed hyperthyroidism. I lost weight, couldn’t sleep, all the signs of hyperthyroidism. I went to a thyroid Dr. for it, and he found thyroid antibodies. He wanted to do a test on my thyroid by injecting my thyroid with iodine. I had done a lot of research and figured it out myself that the iodine from the scan caused the hyperthyroidism. I certainly wasn’t going to let him inject more in it.

    It has been 3 years now, and it has calmed down some but I still can’t sleep well and have other symptoms of hyperthyroidism. However, I will not go back to the thyroid Dr. to let him make it worse. I learned a valuable lesson. NEVER let a Dr. inject anything into your body unless you are dying!!!

  9. Janet
    Tampa Florida

    I knew it! I had 6 CT scans with contrast over three days when my appendix burst in 2008, and no one ever mentioned covering my thyroid gland. 4 years later, I was diagnosed with Hashimoto’s disease, and the only thing I could think of causing that was those CT scans. I haven’t seen any literature until now linking CT scans with Thyroid disease. Thank you so much for publishing this!

  10. Dee

    Why do we need a contrast agent? Iodine has bad side effects and the other option, gadolinium, is even worse. What is the poor patient to do?

  11. Chuck D

    Is there an alternative to iodine for scans?

  12. Sally
    North Carolina

    There is so little information out there about Hyperthyroidism, most articles cover Hypo. I was diagnosed with Hyper and was put on a .25 dose of methimazole. I’m not sure what the “scary” side effects you are talking about are. In my opinion, it’s much better to keep the thyroid and treat with medication rather than having an operation to remove it. The thyroid controls so much of our body, I’d rather have a defective one than none.

  13. Kathryn

    Just recently, my husband suffered a severe panic attack within 12 hours of an MRI with contrast dye. We reported this response to his doctor who didn’t recognize a correlation. I will encourage my husband to be checked for hypothyroidism.

  14. Jane

    Well I had scan with contrast every 6 months for a few years no one placed a thyroid guard on throat and now I am hypo with hashimoto disease life for me will never be the same thanks to the medical field.

  15. Ro
    St. Charles IL

    I had an allergic reaction to iodinated dyes. Before they were done injecting the dye I could see the hives pop up. They shot me up with benadryl. Still don’t have any problems from seafood. How common is an allergic reaction from iodinated dyes?

  16. Judi
    Port St. Lucie, FL

    Until reading this article I had no clue how I developed Hypothyroidism. Back in 1975 I was very ill with Pelvic Inflammatory Disease (PID) from the Dalkon Shield IUD, but no doctor could figure out what was wrong with me.

    Many tests were run on me, including a kidney scan in which they used IVP solution as a contrast die. Afterward I broke out in hives all over my body. Since that day I’ve always noted that I am allergic to IVP solution.

    Some months later I noticed that my hair began falling out dramatically and I felt that my lifeforce was dying. It was my hairdresser who suggested that I was having thyroid problems and should see my doctor.

    She was absolutely right. From that time to now I have been on thyroid medication and am tested every 6 months.

    My hair has never grown back to normal thickness and I have always been puzzled about how I developed the thyroid condition since no one else in my family has ever had thyroid problems. Thank you for the article. Now the mystery is solved.

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