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Healthy living after treatment of childhood, adolescent, and young adult cancer

Thyroid Disease after Cancer Treatment
Some people who were treated for cancer during childhood may develop endocrine (hormone) problems as a resultof changes in the function of a complex system of glands known as the endocrine system.
What is the endocrine system?
The endocrine system is a group of glands
that regulate many body functions including
growth, puberty, energy level, urine production,and stress response. Glands of the endocrine
system include the pituitary, hypothalamus,
thyroid, pancreas, adrenals, ovaries, and testes.
The hypothalamus and pituitary are sometimes
called the “master glands” because they control
many of the other glands in the endocrine
system. Unfortunately, some treatments given
for childhood cancer can damage the endocrine
system, resulting in a variety of problems.

Pituitary gland
Hypothalamus
Thyroid

Pancreas
Adrenal glands

Ovaries

TestesWhat are hormones?
Hormones are chemical messengers that carryinformation from the endocrine glands throughthe bloodstream to the body’s cells. The
endocrine system makes many hormones (suchas growth hormone, sex hormones, adrenaland thyroid hormones) that work together to maintain specific bodilyfunctions.
What is the thyroid gland?
The thyroid gland is located in the lower part of the neck in frontof the throat. The gland makes two hormones, thyroxine (T4) andtriiodothyronine (T3), that play an important role in growth and brain
development and help to regulate the body’s metabolism. The thyroid
gland is controlled by the pituitary, a gland in the brain that makes
thyroid stimulating hormone (TSH). TSH is released from the pituitary
in response to the levels of T4 and T3 in the blood. If the levels arelow, the pituitary makes more TSH to signal the thyroid to increase
the production of thyroid hormones. If T4 and T3 are high, the pituitary
makes less TSH to signal the thyroid gland to slow down production.

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Healthy living after treatment of childhood, adolescent, and young adult cancer

What are the possible late effects?
Damage to the thyroid gland after childhood cancer can be caused by surgical removal of all or part of
the thyroid gland, treatment with tyrosine kinase inhibitors, high doses of MIBG (sometimes used in thetreatment of neuroblastoma), and/or treatment with radiation to the head, brain or neck. This damage
is usually very easy to treat, although it may not show up for years after treatment. Regular check-ups
may help find thyroid problems early so that the proper treatment can be started. Several different typesof thyroid problems may develop including an underactive thyroid (hypothyroidism), overactive thyroid(hyperthyroidism), and growths on the thyroid that may be benign (nodules) or malignant (cancer).
What is hypothyroidism?
Hypothyroidism occurs when the thyroid gland is not active enough. This is the most common thyroid
problem seen in childhood cancer survivors. This can occur if the brain doesn’t make TSH to properly
signal the thyroid gland to work or if the thyroid gland is damaged or has been removed and cannot
make enough thyroid hormone. When the thyroid gland is underactive, thyroid hormone levels are lowand the body’s metabolism slows down.
Signs and symptoms of hypothyroidism may include:• Slowing of normal growth•

Mood changes•

Weight gain•

Feeling cold all of the time•

Dry skin•

Difficulty concentrating•

Brittle hair/hair loss•

Delayed puberty•

Constipation•

Irregular menstrual cycles•

Weakness•

Muscle and joint aches•High cholesterol level•

Poor exercise tolerance•

Feeling tired and listless•

Puffiness around the eyes•

Hoarse voice•

Low heart rate or blood pressure

What is hyperthyroidism?
Hyperthyroidism occurs when the thyroid gland is too active. In this condition thyroid hormone levels arehigh and the body’s metabolism speeds up.
Signs and symptoms of hyperthyroidism may include:• Jitteriness•Feeling hot all of the time•

Anxiety•

Diarrhea•

Problems concentrating•

Weight loss•

Feeling tired•

Irregular menstrual periods•

Muscle weakness•

Bulging or protruding eyes•

Tremors•

Neck tenderness and swelling•

Fast or irregular heartbeat•

Poor exercise tolerance•

Increased sweating

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Healthy living after treatment of childhood, adolescent, and young adult cancer

What are thyroid nodules and thyroid cancer?
Thyroid nodules and thyroid cancer are growths that usually begin as slow-growing, painless lumps in the neck.
Most thyroid growths do not cause any symptoms. They may occur many years after cancer treatment.
Who is at risk for thyroid problems?
People who received radiation that may have affected the thyroid gland directly are at risk for primary hypothyroidism,
compensated hypothyroidism, thyroid nodules, and/or thyroid cancer. People who received radiation to the thyroid
gland in high doses, especially more than 30 Gy or 3000 cGy/rads, are also at risk for hyperthyroidism. The following
radiation fields have the potential to affect the thyroid gland directly:•Head/brain

•

Neck•

Spine (cervical/neck portion)•

Total body irradiation (TBI)

In addition, people who received radioiodine therapy (I-131), high doses of MIBG, or tyrosine kinase inhibitors or had
their thyroid gland partially or completely removed surgically (thyroidectomy) are also at risk for hypothyroidism.
People who received high doses of radiation (30 Gy or 3000 cGy/rads or higher) to the head/brain are at risk for
hypothyroidism.
Other factors that have been shown to increase the risk of thyroid problems after childhood cancer include being:•

Treated with higher radiation doses•

Treated at a young age•

Born with ovaries

Thyroid problems may occur soon after radiation, but generally do not occur until several years later. If treatedpromptly, thyroid problems are easily managed.
What screening is recommended?
All childhood cancer survivors should have a yearly comprehensive health check-up including measurement of height
and weight, examination of the thyroid gland, and blood tests to measure the levels of TSH and T4. During periods ofrapid growth, healthcare providers may recommend more frequent monitoring of thyroid levels.
Survivors at risk for thyroid problems who are planning to become pregnant should have their thyroid levels checked
before attempting pregnancy. It is important to do this before becoming pregnant, as there is a higher chance of
having babies with developmental problems if untreated thyroid disease is present. It is also important to monitor
thyroid levels periodically during pregnancy.
How are thyroid problems treated?
If problems with thyroid levels are identified, you may be referred to an endocrinologist (hormone specialist) for
evaluation and to discuss treatment, such as medication, if needed. If a lump is detected on the thyroid, you may also
be referred to a surgeon or other specialist for further evaluation and management.

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Written by Melissa M. Hudson, MD, St. Jude Children’s Research Hospital, Memphis, TN; and Wendy Landier, PhD, CPNP, Children’s
Hospital of Alabama, Birmingham, AL.
Reviewed by Charles A. Sklar, MD; Debra L. Friedman, MD, Julie Blatt, MD; Joan Darling, PhD; and Susan F. Shaw, RN, MS, PNP.

Additional health information for childhood cancer survivors is available atwww.survivorshipguidelines.org
Note: Throughout this Health Links series, the term “childhood cancer” is used to designate pediatric cancers that may occur during childhood, adolescence, or young adulthood.
Health Links are designed to provide health information for survivors of pediatric cancer, regardless of whether the cancer occurred during childhood, adolescence, or youngadulthood.
Disclaimer and Notice of Proprietary Rights
Introduction to Late Effects Guidelines and Health Links: The Long-Term Follow-Up Guidelines for Survivors of Childhood, Adolescent, and Young Adult Cancers and accompanying Health
Links were developed by the Children’s Oncology Group as a collaborative effort of the Late Effects Committee and Nursing Discipline and are maintained and updated by the Children’s
Oncology Group’s Long-Term Follow-Up Guidelines Core Committee and its associated Task Forces.
To cancer patients (if children, their parents or legal guardians): Please seek the advice of a physician or other qualified health provider with any questions you may have regarding amedical condition and do not rely on the Informational Content. The Children’s Oncology Group is a research organization and does not provide individualized medical care or treatment.
To physicians and other healthcare providers: The Informational Content is not intended to replace your independent clinical judgment, medical advice, or to exclude other legitimate
criteria for screening, health counseling, or intervention for specific complications of childhood cancer treatment. Neither is the Informational Content intended to exclude other reasonable
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