Larry A. Fox, MD
Nemours Children’s Health
Jacksonville, Florida

September 22, 2021

Background
Pediatricians and other practitioners are regularly faced with ordering thyroid function tests (TFTs) in children for a variety of clinical reasons. Sometimes it is a child displaying symptoms suggesting hypothyroidism, development of a goiter, or a decline in growth velocity. It is also common for physicians to order TFTs because the patient is obese, and quite often these thyroid labs are abnormal. With the epidemic of childhood obesity, our clinic is seeing an increasing number of referrals for abnormal TFTs in the setting of obesity. It is important for pediatricians to understand how TFTs are affected by obesity, when thyroid function tests should be ordered, and when a referral is necessary.

The relationship between thyroid function tests and obesity
The effect obesity has on thyroid function has been well documented in adults and children. In most studies, TSH is proportional to BMI. TSH results may be within the assay reference range, but are often slightly above. Thus, it is quite common for obese children (and adults) to have elevated TSH (with slightly increased free or total T3 and normal free T4), suggesting compensated hypothyroidism. In fact, TSH levels are above the reference range in up to 25% of obese children, and several population studies suggest TSH reference ranges need to be adjusted for obesity. Changes in TSH are thought to be mediated by increased leptin causing an increased pituitary release of thyrotropin releasing hormone and a rise in TSH. These changes increase resting energy expenditure and thus are adaptive to the obesity. They do not cause the obesity as evidenced by a decline in TSH with weight loss, either with bariatric surgery (in adults) or lifestyle changes in children and adults.

When should thyroid functions tests be done in an obese child?
Under many clinical circumstances checking TFTs (TSH, free T4) in the setting of obesity is reasonable, such as poor growth, goiter, and/or more specific symptoms suggesting hypothyroidism (such as cold intolerance, generalized dry skin, fatigue or constipation). Simply being overweight or obese (BMI >85th or >95th percentile, respectively) are not symptoms of hypothyroidism and ordering TFTs would not be indicated. Obtaining TFTs in overweight or obese patients without clear indications could lead to unnecessary additional testing, treatment, or referrals. Because the TFT changes are adaptive and do not cause the obesity, treatment is thought not to be necessary.

What should one do if the TSH is abnormal?
If the TSH is elevated above the reference range in an obese individual, the practitioner must decide whether further testing, treatment and/or referral is needed. Because autoimmune disorders are more common in obese individuals, it is reasonable to obtain markers of autoimmune (Hashimoto) thyroiditis (i.e., thyroid peroxidase and thyroglobulin antibody titers). If antibody titers are elevated, referral to a thyroid specialist is reasonable. If the child has a goiter or a nodule is palpable, a thyroid ultrasound would also be informative. If the ultrasound reveals a nodule or cyst, the patient should be referred to a thyroid specialist.
Otherwise, mild elevations in TSH without a goiter do not need treatment and a referral would not be necessary. Instead, rechecking TSH and free T4 in 3-6 months to document the trend in TFTs indicated.

Conclusion
TFTs are commonly abnormal in obese patients, with serum TSH concentrations often above the reference range. These laboratory abnormalities are due to changes in leptin and reflect an adaptation to obesity. Most often the abnormal TFTs do not require treatment. In some circumstances, however, a referral to a thyroid specialist is warranted.

References:
1. Popovic V, Duntas LH. Leptin TRH and ghrelin: influence on energy homeostasis at rest and during exercise. Horm Metab Res. 2005;37:533-7.
2. Reinehr T. Obesity and thyroid function. Mol Cell Endocrinol. 2010;316:165-71.
3. Reinehr T. Thyroid function in the nutritionally obese child and adolescent. Curr Opin Pediatr. 2011;23:415-20.
4. Gertig AM, Niechcial E, Skowrońska B. Thyroid axis alterations in childhood obesity. Pediatr Endocrinol Diabetes Metab. 2012;18:116-9.
5. Valdés S, Maldonado-Araque C, Lago-Sampedro A, et al. Reference values for TSH may be inadequate to define hypothyroidism in persons with morbid obesity: Di@bet.es study. Obesity. 2017;25:788-793.
6. Song R-H, Wang B, Yao Q-M, et al. The impact of obesity on thyroid autoimmunity and dysfunction: a systematic review and meta-analysis. Front Immunol. 2019;10:2349.
7. Gyuricsko E. The “slightly” abnormal thyroid test: What is the pediatrician to do? Curr Probl Pediatr Adolesc Health Care. 2020;50:100770.
8. Oron T, Lazar L, Feldhamer I, et al. Pediatric reference values of TSH should be personalized according to BMI and ethnicity. Eur J Endocrinol. 2020;183:419-426.
9. Tsigalou C, Vallianou N, Dalamaga M. Autoantibody production in obesity: Is there evidence for a link between obesity and autoimmunity? Curr Obes Rep. 2020;9:245-254.
10. Gokosmanoglu F, Aksoy E, Onmez A, et al. Thyroid homeostasis after bariatric surgery in obese Cases. Obes Surg. 2020;30:274-278.
11. Mohareb OA, Saqaaby MA, Ekhzaimy A, et al. The relationship between thyroid function and body composition, leptin, adiponectin, and insulin sensitivity in morbidly obese euthyroid subjects compared to non-obese subjects. Clin Med Insights Endocrinol Diabetes. 2021;14:1179551420988523. eCollection 2021.
12. Aykota MR, Atabey M. Effect of sleeve gastrectomy on thyroid-stimulating hormone levels in morbidly obese patients with normal thyroid function. Eur Rev Med Pharmacol Sci. 2021;25:233-240.

Disclaimer:
The ideas and opinions expressed on the ATA Blogs do not necessarily reflect those of the ATA. None of the information posted is intended as medical, legal, or business advice, or advice about reimbursement for health care services. The mention of any product, service, company, therapy or physician practice does not constitute an endorsement of any kind by ATA. ATA assumes no responsibility for any injury or damage to persons or property arising out of or related to any use of the material contained in, posted on, or linked to this site, or any errors or omissions.

For more information on Thyroid Topics please visit: https://www.thyroid.org/thyroid-information/

The post Thyroid Health Blog: Obesity and Thyroid Function Tests in Children appeared first on American Thyroid Association.

Siobhan T. Pittock, MD
Mayo Clinic
Rochester, MN
July 15, 2021

Increasing incidence of thyroid cancer
The incidence of thyroid cancer in all ages has increased significantly over the past 4 decades while the mortality rate has remained relatively unchanged. In adults, the increased incidence has largely been attributed to increased use of diagnostic imaging and fine needle biopsies and has resulted in diagnosis of earlier staged cancers. This change has resulted in a significant change in recommendation for management of smaller papillary carcinomas (measuring <1-1.5cm) where active observation may be the best course. (1)

Has this increase in incidence been mirrored in pediatrics?
Yes. The increase in diagnosis of pediatric thyroid cancer (predominantly papillary thyroid cancer) has been dramatic over the past 40 years but especially over the last 15 years. The incidence of thyroid cancer has increased from 0.48 to 1.33 per 100,000 person years from 1973 to 2018 (2). Recent studies suggest that the rate of increasing incidence has changed significantly over time. Bernier et al show an annual percent change (APC) in incidence of 4.43% per year between 1998 and 2013 (3). Qian et al report the increase has been far more recent with a dramatic increase in the APC from 1.1% per year between 1973 and 2006 to 9.5% per year between 2006 and 2013 (4).

Both groups show the increase as mainly occurring in the 10-19-year-old age group, in both sexes and all racial groups. The fact that both groups found similar increases in incidence for large and small tumors and for those with local or regional disease argues against this simply representing over diagnosis or diagnosis of smaller less clinically relevant tumors.

What should I tell my patients?
Since most known risk factors for thyroid cancer are not modifiable (e.g. age, female sex, family history), we have limited opportunities for counselling our patients. However, one thing we can do is to avoid overuse of imaging studies including CT scans since exposure to ionizing radiation especially at a young age is a known risk factor for thyroid (and other) cancers. Increased risk for thyroid cancer may be yet another reason to avoid excessive weight gain because obesity has been linked to an increased risk of thyroid cancer (5). The fact that the increasing incidence of thyroid cancer has mirrored the obesity epidemic experienced in the developed world lends further credence to this evidence (6).

What should we do?
Thyroid cancer in pediatric patients is not a rare entity, in fact it is the most common non-CNS solid tumor in childhood (2). The most important thing we can do is raise awareness of its existence with patients and primary care providers. Palpation of the neck for the presence of nodules needs to be part of every routine physical exam in childhood. While raising awareness, we also need to avoid excessive intervention for a condition which continues to have an excellent prognosis (7).

References:
1. The changing incidence of thyroid cancer. Kitahara CM, Sosa JA.Kitahara CM, et al. Nat Rev Endocrinol. 2016 Nov;12(11):646-653. doi: 10.1038/nrendo.2016.110.
2. https://seer.cancer.gov/ accessed June 15 2021
3. Trends in pediatric thyroid cancer incidence in the United States, 1998-2013. Marie-Odile Bernier , Diana R Withrow , Amy Berrington de Gonzalez , Clara J K Lam , Martha S Linet , Cari M Kitahara , Meredith S Shiels. Cancer. 2019 Jul 15;125(14):2497-2505. doi: 10.1002/cncr.32125. Epub 2019 Apr 23
4. Pediatric Thyroid Cancer Incidence and Mortality Trends in the United States, 1973-2013. Z Jason Qian , Michael C Jin , Kara D Meister , Uchechukwu C Megwalu. JAMA Otolaryngol Head Neck Surg . 2019 Jul 1;145(7):617-623. doi: 10.1001/jamaoto.2019.0898.
5. Schmid, D., Ricci, C., Behrens, G. & Leitzmann, M. F. Adiposity and risk of thyroid cancer: a systematic review and meta-analysis. Obes. Rev. 16, 1042–1054 (2015)
6. Ng, M. et al. Global, regional, and national prevalence of overweight and obesity in children and adults during 1980–2013: a systematic analysis for the Global Burden of Disease Study 2013. Lancet 384, 766–781 (2014).
7. Papillary Thyroid Carcinoma (PTC) in Children and Adults: Comparison of Initial Presentation and Long-Term Postoperative Outcome in 4432 Patients Consecutively Treated at the Mayo Clinic During Eight Decades (1936-2015). Hay ID, Johnson TR, Kaggal S, Reinalda MS, Iniguez-Ariza NM, Grant CS, Pittock ST, Thompson GB.Hay ID, et al. World J Surg. 2018 Feb;42(2):329-342. doi: 10.1007/s00268-017-4279-x.World J Surg. 2018. PMID: 29030676

Disclaimer:
The ideas and opinions expressed on the ATA Blogs do not necessarily reflect those of the ATA. None of the information posted is intended as medical, legal, or business advice, or advice about reimbursement for health care services. The mention of any product, service, company, therapy or physician practice does not constitute an endorsement of any kind by ATA. ATA assumes no responsibility for any injury or damage to persons or property arising out of or related to any use of the material contained in, posted on, or linked to this site, or any errors or omissions.

For more information on Pediatric Thyroid Topics please visit: https://www.thyroid.org/thyroid-information/

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Preguntas frecuentes

Qué es lo que preocupa sobre la glándula tiroides y la radiación?

La glándula tiroides de los niños es particularmente sensible a la radiación. La exposición a la radiación causa distintos problemas tiroideos que incluyen una glándula hipoactiva (hipotiroidismo), nódulos tiroideos y cáncer de tiroides. Cuanto más joven es el niño al recibir la radiación, mayor es el riesgo para que ocurran estos trastornos.

Cómo puede exponerse un niño a la radiación?

La exposición a la radiación puede ser accidental, o puede ser parte de un tratamiento médico. La exposición accidental puede ocurrir durante un accidente nuclear (como ha ocurrido en la planta nuclear de Chernobyl, Rusia). El tratamiento con radiación fue indicado por distintas entidades médicas como amigdalitis entre los años 1940 y 1960, actualmente no se utiliza más para estos casos. Pero, el tratamiento con radiación es esencial para algunos cánceres que afectan a los niños. Estos tumores no pueden ser completamente tratados sin causar alguna exposición a la radiación a la glándula tiroides.

Cuanto tiempo después de la radiación ocurren los problemas de la glándula tiroides?

Los problemas tiroideos pueden ocurrir tan pronto como algunos años (2-3 años para hipotiroidismo) o en un período más largo (8-50 años para nódulos y cáncer de tiroides) luego de la exposición a la radiación.

Pueden los adultos ser afectados por la exposición a la radiación?

Si bien la glándula tiroides de los adultos es menos sensible a la radiación, también puede ser afectada, especialmente durante el tratamiento con radiación para los cánceres de cabeza y cuello. Tanto como hipotiroidismo, nódulos y cáncer de tiroides pueden desarrollarse en los adultos luego de la exposición a la radiación.

Que debe hacerse si un niño ha sido expuesto a radiación?

Es muy importante para cualquier individuo que ha expuesto a la glándula tiroides a radiación que tenga consultas frecuentes con el médico. Existe un excelente tratamiento medico para hipotiroidismo y cáncer de tiroides. Los médicos tienen varios y buenos métodos para monitorear los nódulos tiroideos.

El cáncer de tiroides es más difícil de tratar en alguien que ha recibido radiación?

Existen algunas evidencias que indican que el cáncer de tiroides puede extenderse más al tiempo de diagnóstico en los pacientes que han recibido radiación. Sin embargo, el tratamiento habitual para el cáncer de tiroides sigue siendo muy efectivo, y las tasas de supervivencia son similares en los pacientes que no han recibido radiación como en los que sí han recibido.

Cuanto tiempo debe el medico controlar a un paciente que ha recibido tratamiento con radiación?

Debido a que los problemas tiroideos pueden ocurrir varios años después que se ha recibido el tratamiento con radiación, se recomienda el seguimiento de por vida. Si a un paciente se le diagnostica hipotiroidismo luego del tratamiento con radiación el tratamiento con hormona tiroidea es para el resto de su vida.

Informacion adicional

Mas detalles sobre este y otro temas relacionados estan disponibles en la seccion informacion para pacientes del sitio web de la American Thyroid Association www.thyroid.org.

Radiación de Cabeza y Cuello en la Infancia FAQ para guardar e imprimir (PDF File, 260 KB)

Radiación de Cabeza y Cuello en la Infancia FAQ para guardar e imprimir (PDF File, 137 KB)

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Qué es lo que preocupa respecto a radiación y glándula tiroides?

La glándula tiroides puede ser afectada por su exposición a la radiación. La glándula tiroides de los niños es especialmente sensible a la radiación, mucho más que la glándula tiroides de un adulto. La exposición a la radiación puede causar diferentes problemas tiroideos, que incluyen una glándula hipoactiva (hipotiroidismo), nódulos tiroideos, y cáncer de tiroides. Cuanto más joven el niño que se expone a la radiación, mayor el riesgo a que ocurran estos problemas. Si la exposición a la radiación ocurre cuando son mayores de 20 años, el riesgo es el mismo al de la exposición a la radiación de los adultos. El riesgo de estos problemas tiroideos es probablemente mayor con grandes dosis de radiación.

Como puede un niño exponerse a la radiación?

La exposición a la radiación puede ser accidental, o puede ser parte de un tratamiento médico.

La exposición accidental ha ocurrido con la liberación de iodo radioactivo (I-131, ver folleto de Iodo radioactivo) durante accidentes nucleares, como el de la planta nuclear de Chernobyl (Rusia) en 1986, o durante pruebas con bombas atómicas (1951-1958, Islas Marshall;1951–1970, Nevada). Si Ud. era un niño en el tiempo del testeo con bombas atómicas en los sitios mencionados, puede encontrar si estuvo potencialmente expuesto en el siguiente sitio Web: https://ntsi131.nci.nih.gov/.

El tratamiento con radiación ha sido utilizado en el pasado (años1940-1960) para tratar enfermedades benignas como la tiña, amigdalitis, agrandamiento del timo y de ganglios linfáticos. Este tipo de tratamiento medico no se utiliza en la actualidad. Sin embargo, el tratamiento con radiación sigue siendo una parte muy importante del tratamiento para ciertos tipos de cáncer de la infancia, especialmente los que comprometen la cabeza y el cuello, como los linfomas no Hodgkin, la enfermedad de Hodgkin, leucemia linfoblástica aguda, rabdomiosarcoma, neuroblastoma, carcinoma nasofaríngeo y sarcoma de Ewin. Para todos estos cánceres, no se puede completar bien el tratamiento sin causar alguna exposición a la radiación a la glándula tiroides.

Cuanto tiempo después de la exposición a la radiación ocurren los problemas tiroideos?

Hipotiroidismo (ver el folleto de hipotiroidismo)
Una glándula hipoactiva puede desarrollarse desde unos meses a varios años luego del tratamiento con radiación. Sin embargo, lo más probable es que ocurra 2-3 años luego del tratamiento. Esta situación es efectivamente y fácilmente tratada con hormona tiroidea.

Nódulos Tiroideos (ver el folleto de nódulos tiroideos)
Los nódulos tiroideos ocurren cuando hay un crecimiento de células tiroideas en un bulto dentro de la glándula tiroides. Generalmente se diagnostican varios años después del tratamiento radiante (8 a 12 años). Pueden ser detectados por el medico al hacer el examen físico del cuello y de la glándula tiroides, o pueden ser vistos durante un estudio con ecografía del cuello o de la glándula tiroides.

Cáncer de Tiroides (ver folleto de cáncer de tiroides)
El cáncer de tiroides puede diagnosticarse en cualquier momento a partir de los 5 a 20 años luego de la radiación, 10 años post radiación es el tiempo más común de diagnóstico. Sin embargo este período de tiempo puede extenderse a 40 a 50 años luego de la exposición.

Los adultos pueden ser afectados por la exposición a la radiación?

Mientras que la glándula de los adultos es mucho menos sensible a la radiación, también puede ser afectada, especialmente durante la radioterapia para los cánceres de cabeza y cuello. El hipotiroidismo, los nódulos tiroideos y el cáncer de tiroides también pueden producirse en adultos luego de la exposición a la radiación.

Cómo se detectan los problemas tiroideos?

El hipotiroidismo puede ser fácilmente detectado por un examen de sangre. Los pacientes pueden o no tener síntomas de una glándula hipoactiva.

Los nódulos tiroideos pueden ser detectados cuando el medico examina la glándula tiroides a la palpación, o pueden ser detectados al utilizar un ecógrafo. Una vez que se la ha encontrado al paciente un nódulo tiroideo, el medico va a controlar regularmente el nódulo para ver ha crecido, o va a solicitar una punción con aguja fina del mismo (ver el folleto de nódulo tiroideo).

El cáncer de tiroides es más frecuente hallarlo en nódulos tiroideos cuando el paciente ha sido expuesto a la radiación en su infancia. Puede diagnosticarse en 15-30% de los nódulos tiroideos que se han desarrollado luego del tratamiento radiante durante la infancia. Puede ser detectado por una punción con aguja fina de las células tiroideas del nódulo. Este procedimiento es recomendable para todos los nódulos tiroideos que pueden palparse en el examen médico, los nódulos que han crecido de tamaño, y ciertos nódulos cuyas características son sospechosas.

Cual es el tratamiento para los problemas de tiroides en pacientes que han tenido exposición a la radiación de niños?

Debido a que los problemas tiroideos pueden ocurrir muchos años después de la exposición inicial, es muy importante para un individuo que ha recibido radiación de niño que tenga controles regulares con un médico.

El hipotiroidismo puedes ser fácilmente tratado con hormona tiroidea, exactamente como el hipotiroidismo debido a otras causas (ver el folleto de hipotiroidismo).

Los nódulos tiroideos de pacientes que han sido expuestos ala radiación en su infancia deben ser monitoreados regularmente y muchos de esos nódulos requieren ser punzados para asegurarse que no existe un cáncer de tiroides (ver el folleto de nódulos tiroideos).

Si se encuentra un cáncer de tiroides en un nódulo de alguien que ha sido expuesto a la radiación en su infancia, el tratamiento es el mismo que se indica a otro paciente con cáncer de tiroides (ver el folleto de cáncer de tiroides). Usualmente el primer paso es la cirugía, a veces el iodo radioactivo puede ser necesario. Y siempre se utiliza el tratamiento con hormona tiroidea.

El cáncer de tiroides es más difícil de tratar en alguien que ha recibido radiación?

Hay algunas evidencias que el cáncer de tiroides pudo haberse extendido más al tiempo de diagnóstico en pacientes que han recibido tratamiento con radiación. Sin embargo, el tratamiento habitual para el cáncer de tiroides es muy efectivo y las tasas de sobrevida son similares que para los pacientes que no han recibido tratamiento con radiación.

Cuanto tiempo debe el médico seguir a alguien que ha recibido tratamiento con radiación?

Debido a que los problemas de tiroides pueden ocurrir muchos años luego del tratamiento con radiación, se recomienda un seguimiento de por vida. Si un paciente desarrolla hipotiroidismo luego de la radioterapia, va a precisar tratamiento con hormona tiroidea por el resto de su vida.

Informacion Adicional

Mas detalles sobre este y otro temas relacionados estan disponibles en la seccion informacion para pacientes del sitio web de la American Thyroid Association www.thyroid.org.

El folleto de Irradiación de Cabeza & Cuello en la Infancia para guardar e imprimir (PDF
File, 446 KB)

El folleto de Irradiación de Cabeza & Cuello en la Infancia para guardar e imprimir (PDF
File, 188 KB)

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Frequently Asked Questions

What is the concern about the thyroid gland and radiation?

The thyroid glands of children are especially sensitive to radiation. Radiation exposure appears to cause a number of different thyroid problems including an underactive thyroid (Hypothyroidism), thyroid nodules, and thyroid cancer. The younger the child is when the radiation exposure occurs, the greater the risk is of these problems occurring.

How can a child’s thyroid be exposed to radiation?

Radiation exposure can be accidental, or it can be part of medical treatment. Exposure could occur during a nuclear accident (as has previously occurred with the Russian Chornobyl nuclear power plant accident). Radiation treatment was given for medical conditions such as enlargement of the tonsils in the 1940-1960s; however, this is no longer done. Radiation treatment is an essential part of the treatment of some cancers that affect children. With these cancers, the cancer cannot be completely treated without causing some radiation exposure to the thyroid gland.

How long after radiation exposure do thyroid problems occur?

Thyroid problems may occur as soon as a few years (2-3 years for hypothyroidism) or as long as many years (8-12+ years for thyroid nodules and thyroid cancer) after the radiation exposure.

Can adults be affected by radiation exposure?

While the adult thyroid gland is much less sensitive to radiation, it too may be affected, especially during radiation therapy for head and neck cancers. Hypothyroidism, thyroid nodules and thyroid cancer all can occur after radiation exposure in adults.

If a child has been exposed to radiation, what should be done?

It is very important for anyone who has received radiation exposure to the thyroid gland to have regular visits with a physician. There is excellent medical treatment for hypothyroidism and thyroid cancer. Physicians also have good ways of monitoring or checking on thyroid nodules.

Is thyroid cancer harder to treat in someone that has been treated with radiation?

There is some evidence that thyroid cancer may have spread more by the time it is detected in patients who have had radiation treatment. However, the usual treatment for thyroid cancer is still very effective and survival rates are similar to patients that have not received radiation treatment.

How long should a physician follow someone who has had radiation treatment?

Because thyroid problems can occur many years after the radiation therapy was given, life-long monitoring is recommended. If a patient develops hypothyroidism after radiation treatment they will need life-long treatment with thyroid hormone.

Childhood Head and Neck Irradiation FAQ for Saving and Printing (PDF File, 256 KB)

Childhood Head and Neck Irradiation FAQ for Saving and Printing (PDF File, 133 KB)

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What is the thyroid gland?

The thyroid gland is a butterfly-shaped endocrine gland that is normally located in the lower front of the neck. The thyroid’s job is to make thyroid hormones, which are secreted into the blood and then carried to every tissue in the body. Thyroid hormone helps the body use energy, stay warm and keep the brain, heart, muscles, and other organs working as they should.

Exposure Concerns, Detection and Treatment

The thyroid gland can be affected by exposure to radiation. The thyroid glands of children are especially sensitive to radiation, much more so than the thyroid gland of an adult.

What is the concern about the thyroid gland and radiation?

The thyroid gland can be affected by exposure to radiation. The thyroid glands of children are especially sensitive to radiation, much more so than the thyroid gland of an adult. Radiation exposure appears to cause a number of different thyroid problems, including an underactive thyroid (hypothyroidism), thyroid nodules, and thyroid cancer. The younger the child is when the radiation exposure occurs, the greater is the risk of these problems occurring. If radiation exposure occurs when they are older than 20 years, their risk is the same as radiation exposure to adults. The risk of these thyroid problems is probably also greater with larger doses of radiation.

How can a child be exposed to radiation?

Radiation exposure can be accidental, or it can be part of medical treatment.

Accidental exposure has occurred with the release of radioactive iodine (I-131, see Radioactive Iodine brochure) during nuclear accidents, such as during the Russian Chornobyl nuclear power plant accident in 1986, or during atomic bomb testing (1951-1958, Marshall Islands; 1951–1970, Nevada Test Site). If you were a child in the time frame of atomic bomb testing at the Nevada Test Site, you can discover if you were potentially exposed to radiation at the following website: http://ntsi131.nci.nih.gov/.

Radiation therapy has been used in the past (1940– 1960s) to treat benign conditions such as ring worm, enlarged thymus, enlarged tonsils, and enlarged lymph nodes. These types of medical treatments are no longer used. However, radiation therapy is still a very important part of the treatment of some types of childhood cancers, especially those involving the head and neck. These serious cancers include non-Hodgkin’s lymphoma, Hodgkin’s disease, acute lymphoblastic leukemia, rhabdomyosarcoma, neuroblastoma, nasopharyngeal carcinoma, and Ewing sarcoma. For all these cancers, the cancer cannot be completely treated without causing some radiation exposure to the thyroid gland.

How long after radiation exposure do thyroid problems occur?

There can be many reasons why the cells in the thyroid gland can’t make enough thyroid hormone. Here are the major causes, from the most to the least common.

Hypothyroidism (see Hypothyroidism brochure)

• An underactive thyroid can develop from a few months to many years after radiation therapy. However, it is most likely that this will occur 2 –3 years after the treatment. This condition is effectively and easily treated with thyroid hormone.

Thyroid nodules (see Thyroid Nodule brochure)

• Thyroid nodules occur when there is a growth of thyroid cells into a lump within the thyroid gland. Thyroid nodules are usually noticed several years (typically 8 –12 years) after radiation treatment. They can be detected by a physician when he/she performs a physical examination of the neck and thyroid gland, or they can be seen using an ultrasound examination (picture of the thyroid gland obtained using sound waves).

Thyroid cancer (see Thyroid Cancer brochure)

• Thyroid cancer may be found anywhere from 5 – 20 years after radiation treatment was given, although about 10 years after the treatment is the most common time. It can also be seen as late as 40-50 years after exposure.

Can adults be affected by radiation exposure?

While the adult thyroid gland is much less sensitive to radiation, it too may be affected, especially during radiation therapy for head and neck cancers. Hypothyroidism, thyroid nodules and thyroid cancer all can occur after radiation exposure in adults.

How can thyroid problems be detected?

Hypothyroidism can be easily detected by a blood test. Patients may or may not have symptoms of an underactive thyroid.

Thyroid nodules can either be detected when a physician examines the thyroid gland by touch, or they can be detected using an ultrasound machine. Once a patient has been found to have a thyroid nodule, a physician will regularly re-examine the patient to see if the nodule has increased in size and/or may perform a fine needle aspiration biopsy of the nodule (see Thyroid Nodule brochure).

Thyroid cancer is more frequently found in thyroid nodules when the patient also had radiation exposure during childhood. Thyroid cancer may be found in about 15 – 35% of thyroid nodules that develop after radiation treatment or exposure during childhood. Thyroid cancer can be detected by a fine needle aspiration biopsy of thyroid cells from the nodule. This procedure is recommended for all thyroid nodules that can be felt on physical examination, nodules that increase in size, and certain other nodules with features that are worrisome.

What is the treatment for thyroid problems in patients who have received radiation exposure as children?

Since thyroid problems may occur many years after the initial exposure, it is very important for an individual who has received radiation exposure as a child to have regular visits with a physician.

Hypothyroidism can be easily treated with thyroid hormone, exactly as hypothyroidism due to other causes is treated (see Hypothyroidism brochure).

Thyroid nodules in patients with childhood radiation exposure need to be monitored on a regular basis and many nodules require fine needle aspiration biopsy to make sure a thyroid cancer is not present (see Thyroid Nodule brochure).

If a thyroid cancer is found in a thyroid nodule of someone who was exposed to radiation as a child, the treatment is the same as any other patient found to have thyroid cancer (see Thyroid Cancer brochure). Usually thyroid surgery is a first step. Radioactive iodine may be necessary. Use of thyroid hormone treatment is always needed.

Is thyroid cancer harder to treat in someone that has been treated with radiation?

There is some evidence that thyroid cancer may have spread more by the time it is detected in patients who have had radiation treatment. However, the usual treatment for thyroid cancer is still very effective and survival rates are similar to patients that have not received radiation treatment.

How long should a physician follow someone who has had radiation treatment?

Because thyroid problems can occur many years after the radiation therapy was given, life-long monitoring is recommended. If a patient develops hypothyroidism after radiation treatment they will need life-long treatment with thyroid hormone.

Further Information

Further details on this and other thyroid-related topics are available in the patient information section on the American Thyroid Association^® website at www.thyroid.org.

Childhood Head & Neck Irradiation Brochure for Saving and Printing (PDF File, 446KB)

Childhood Head & Neck Irradiation Brochure for Saving and Printing (PDF File, 189 KB)

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