Radiation Treatment and Your Thyroid
By Jeffrey W. Cash, DDS
Radiation Treatment and Your Thyroid Gland
How radiation treatment and your thyroid gland interact can change your systemic health. Learn why it is important to monitor your thyroid gland during and after your treatment. Let us take a closer look at why this is so significant.
What Does the Thyroid Gland Do?
The thyroid gland is located in the neck and is situated close to the voice box. It produces hormones that are very important to keep our body’s metabolism in balance. Functions that are vital to our bodies such as breathing, heart rate, temperature, and muscle strength are all influenced by the thyroid. Also in this area are the parathyroid glands which control the levels of calcium in our blood so nerves and muscles operate correctly.
With all that the thyroid and parathyroid glands manage, it is easy to understand why even small changes to them can lead to big problems.
What Damages the Thyroid?
Damage to the thyroid gland during head and neck cancer treatment is related to the location of the tumor. This is where surgery and radiation happen. A tumor that requires a laryngectomy will likely have part of the thyroid removed simply because it is so close to the voice box. Then, the standard portals (fields) of radiation often include the thyroid to lower the chance of any cancer cells surviving.
Both the surgery and radiation damage the thyroid and weaken it’s ability to work. The progressive scarring from radiation harms the gland until it cannot perform adequately. The end result is hypothyroidism.
Does Everyone Get Thyroid Damage?
Treating a head and neck cancer with radiation requires a significant dose measured in Grays. One study mentions that hypothyroidism can be expected with 26 or more Grays. The current standard radiation given for head and neck tumors can range from 50-60+ Grays depending on the tumor type.
Literature shows hypothyroidism is linked with radiation and can be expected in 48-67% of patients over time.
What Does This Mean for Me?
Having hypothyroidism slows the body’s normal rate of functioning, leaving people feeling less mentally alert and fatigued. In some cases, it can also contribute to depression. Because of this, you should have your thyroid checked at your doctor’s visits as often as recommended.
You should get a check of your thyroid before radiation starts for a baseline reading. Check this again with your doctor about 3 months after treatment is finished. Keep in mind that it may take a long time for the thyroid to slow down. Regularly checking should continue for many years after radiation has finished. The American Cancer Society Journals note: “The screening interval for these patients is unknown; however, an annual or semiannual screening for TSH level seems reasonable given the long latent interval that frequently occurs.”