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Radiation and Thyroid Hormone


I completed 15 sessions of radiation therapy to my chest wall, axilla and supra-clavicular area on 19th November. Last week I did a thyroid panel blood test which shows that despite not altering my thyroid medication, my Free Thyroxine levels have dropped to way below the bottom of the reference range. It used to be in the top third of the reference range. It's never been this low before.

My Free T3 had also dropped but was still within the reference range. (I take thyroid meds that contain both T3 and T4, which is likely why my body used up the T4 but still had some T3 left in the blood)

Can radiotherapy affect either the thyroid gland itself, or the body's need for thyroid hormones?


  • ratherbesailing
    ratherbesailing Member Posts: 118
    edited December 2021

    Too-Ticky -

    With supraclavicular nodes irradiated, your thyroid almost certainly took a bit of a hit. Most patients are fine but, if the thyroid is affected, it may not become apparent for several years. Radiation oncologists seem to never mention thyroid as an organ at risk.

    My thyroid went haywire shortly after I completed radiation - my TG antibodies were very high. Fortunately, it did settle down.

    Hoping your does, too.

  • sabbymama
    sabbymama Member Posts: 82
    edited December 2021

    I also completed 15 rounds of accelerated radiation to my chest, axillary and supraclavicular regions and dealt with some thyroid issues. I was not on any medication at the time, but I had been diagnosed with Hashimotos many years before my BC diagnosis and I had a 9mm nodule on my left thyroid, which we were closely monitoring. My ATPO has always been high in the 300-400 range. I completed rads in October and in January I started to have some serious heart palpitations and visited the cardiologist and the endocrinologist and it was discovered that my TSH was .001, my ATPO jumped to 780, and a nuclear scan showed my nodule had become autonomously hyperactive. We discussed removing that portion of my thyroid or irradiating it in a couple of months after repeating some tests. Oddly enough, within two months, my TSH went back to normal range 1.1 and an ultrasound showed 3 new nodules, but my T3 and T4 remained normal the whole time. Both my endo and my RO insist that it shouldn't have been the radiation that caused the problem, but I do question it. The only other thing that might have caused the "blip" could be the Zometa infusion I had in December? The ATPO remains high as it always did and my last blood draw showed that my T3 was a bit low, but otherwise things have been "normal". Hopefully your situation will resolve in time ;). Take care!

  • Too-Ticky
    Too-Ticky Member Posts: 19
    edited January 2022

    Thanks for your replies, @RatherBeSailing and @Sabbymamma

    I'm glad you both found that your thyroid glands settled down again. I would normally judge when to do a blood test for my thyroid by my symptoms, heart rate and temperature. But I started Tamoxifen a few weeks ago so those things are all over the place! I think I'll do another blood test in a month or so to see if anything's improved.