What is a thyroid guard and why have you not been asked to wear one when getting certain types of X-rays? The medical community is divided as to whether or not a thyroid guard is necessary. But since studies show that thyroid cancer is related to radiation exposure, most patients are requesting the extra protection. (1) (2)
Over the last two decades, incidence of thyroid cancer has been steadily increasing. In fact, thyroid cancer is the fastest growing form of cancer in the United States. And while thyroid cancer is more common in women than in men, rates are rising in both men and women. (3) (4)
While researchers are still baffled as to exactly why thyroid cancer rates are rising, they have identified several risk factors. Risk factors are possibilities -- such as lifestyle, age, or family history -- that increase a person's risk for developing a certain disease. What are the risk factors of thyroid cancer?
The biggest risk factor is radiation exposure. For most of us, this means CT scans of the head and neck area, mammograms, and dental X-rays. The risk factor of radiation is especially great if exposure happens during childhood. (2)
Dental X-rays and mammograms expose the body to radiation. While the amount of exposure to the thyroid is minimal, it is enough that even the American Dental Association (ADA) recommends that a thyroid guard be worn with the customary leaded apron during an X-ray exam because it can reduce the risk of harmful radiation. (5) (6)
Women, consider this: Both dental X-rays and mammograms are routine. This means that most women are exposed to one, if not both forms of radiation, at least once per year.
Radiation exposure alone does not account for the rising prevalence of thyroid cancer.
Do you believe that an increase of radiation exposure means that more people are getting thyroid cancer? Before you answer this question, first consider the other big risk factors of thyroid cancer:
- Gender. The research shows that women, more than men, are more likely to get thyroid cancer. (7)
- History of a thyroid disorder. This means specifically goiter and thyroid nodules, but also includes a history of hypothyroidism. (8)
The other risk factors that are associated with thyroid cancer are worth paying attention to. Most researchers will agree that radiation exposure alone does not account for the rising prevalence of thyroid cancer.
Thyroid cancer shows up in thyroid nodules. Thyroid nodules are growths or lumps that are found in an otherwise healthy thyroid gland. Thyroid nodules are common. So common, in fact, that the diagnosis of thyroid nodule is the most diagnosed endocrine problem in the United States. More than 50 percent of the U.S. population has them. (9) Many thyroid nodules are found accidently during screenings that are not related to thyroid cancer.
What does a cancerous or malignant nodule look like?
- Cancer is commonly detected in a single nodule, rather than a cluster of several.
- The nodule is filled with blood vessels and tissue, rather than just fluid.
- The edges of cancerous nodule are unclear.
The good news is that most thyroid nodules are completely harmless. Only a very small percentage of thyroid nodules turn out to be cancerous.
Another common thyroid disorder linked to thyroid cancer is goiter. (10) A goiter is an overall swelling of the thyroid gland and can develop for several reasons. While most people associate goiter with iodine deficiency, a goiter can develop:
- During pregnancy
- From autoimmune-related Hashimoto's disease
- From environmental toxins
Both thyroid nodules and goiter are associated with poor thyroid function. One big indicator that the thyroid is not doing its job: High levels of TSH (thyroid-stimulating hormone).
The thyroid gland influences things like metabolism and body temperature. It is extremely sensitive to other hormones in the body, immune system disorders, and to toxins that we pick up from the environment, food, or from pharmaceutical drugs.
Once the thyroid begins to malfunction, it stops producing thyroid hormones like it should. What happens? The brain sends out a stronger message to produce more thyroid hormone, which means an increase in TSH.
When your doctor screens the health of your thyroid, the No. 1 diagnostic indicator is high TSH. If TSH is high, your brain is shouting out the message loud and clear: Produce more thyroid hormone! Hypothyroidism, or an underactive thyroid, can cause high levels of TSH.
A recent study shows a strong and direct link between thyroid cancer and high levels of TSH. Other studies show that a history of a thyroid imbalance, even several years prior to diagnosis, is positively linked to thyroid cancer. (11)
Steps that you can take to reduce your risk of thyroid cancer:
While the overall cure rate of the most common forms of thyroid cancer is extremely high (close to 100 percent), we still want to minimize our risk of thyroid cancer. (12)
Wear a thyroid guard. Decades of research and studies tell us that radiation exposure to the head, neck, and torso increases the risk for thyroid cancer. While the medical community is divided on how much radiation exposure is safe or dangerous, your physician or dentist does carry the thyroid guard. So ask for it.
Run a complete thyroid panel. Thyroid cancer is directly related to high levels of TSH. Even if you do not have a history of hypothyroidism or goiter, visit your primary care provider regularly and check on the health of your thyroid. This means asking for a complete thyroid exam that includes checking levels of TSH, thyroid hormones T4 and T3, and thyroid antibodies.
Be careful of the Iodine hype. Iodine, while central to the production of thyroid hormones T3 and T4, can actually make some thyroid conditions worse. This is because iodine speeds up the production of a thyroid enzyme. If the body has developed autoimmunity to this enzyme, which happens in the case of Hashimoto's thyroiditis, then this will increase the inflammatory cascade.
Heal the Gut. Populating the gut with beneficial bacteria from fermented foods and probiotic beverages can help increase thyroid health. Gut flora convert 20 percent of T4 into usable T3.(13)
1. G. Wingren, et al. Diagnostic X-ray exposure and female papillary thyroid cancer: a pooled analysis of two Swedish studies. European Journal of Cancer Prevention. 1997 December; 6 (6).
2. Elaine Ron, et al. Thyroid Cancer after Exposure to External Radiation: A Pooled Analysis of Seven Studies. Radiation Research. 1995 March; 141 (3): 259-277.
3. Louise Davies, et al. Increasing Incidence of Thyroid Cancer in the United States, 1973-2002. JAMA. 2006; 295 (18): 2164 - 2167.
4. American Cancer Society: Cancer Facts and Figures 2012. Atlanta, Ga: American Cancer Society, 2012.
5. X-Rays: Oral Health Topics. American Dental Association. Available at: www.ada.org. Accessed Jan 31, 2012.
6. David R. Myers, et al. Radiation exposure during panoramic radiography in children. Oral Surgery, Oral Medicine, Oral Pathology. 1978 October; 46 (4): 588 -593.
7. Jemal A, Siegel R, Ward E, et al. Cancer statistics, 2009. CA Cancer J Clin. 2009; 59: 225 - 249.
8. S. Preston-Martin, L. Bernstein, M. C. Pike, A. A. Maldonado, and B. E. Henderson. Thyroid cancer among young women related to prior thyroid disease and pregnancy history. Br J Cancer. 1987 February; 55 (2): 191 - 195.
9. Ezzat S, Sarti DA, Cain DR, Braunstein GD. Thyroid incidentalomas. Prevalence by palpation and ultrasonography. Arch Intern Med 1994; 154: 1838 - 1840.
10. McTiernen A. M., et al. Incidence of thyroid cancer in women in relation to previous exposure to radiation therapy and history of thyroid disease. J. Natl. Cancer Inst. 1984 Sep; 73 (3): 575 - 581.
11. Haymart MR, Repplinger DJ, Leverson GE, et al. Higher serum thyroid stimulating hormone level in thyroid nodule patients is associated with greater risks of differentiated thyroid cancer and advanced tumor stage. J Clin Endocrinol Metab 2008; 93: 809 - 814.
12. Hundahl SA, Fleming ID, Fremgen AM, Menck HR. A National Cancer Data Base report on 53,856 cases of thyroid carcinoma treated in the U.S., 1985 - 1995.
13. de Herder, WW, et al. On the enterohepatic cycle of triiodothyronine in rats; importance of the intestinal microflora. Life Sci. 1989; 45 (9): 849 - 56.
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