Thyroid Issues After Childhood Cancer Treatment
What’s the risk?
The thyroid gland is located in the neck. It produces hormones that are important for controlling metabolism, growth, and development. The thyroid's production of these hormones is controlled by the pituitary gland, which is located in the brain. Radiation fields that include the brain, thyroid gland, or come close to the thyroid gland (head & neck, upper spine and upper chest) are at risk for a variety of thyroid problems. In addition, survivors treated with radioiodine therapy (I-131) or MIBG therapy are at risk. Thyroid problems can include hypothyroidism (underactive thyroid), hyperthyroidism (overactive thyroid), and thyroid nodules/tumors.
Although risk continues for the life of a survivor, peak incidence of hypo and hyperthyroidism has most often been seen at 2-5 years after treatment, while thyroid nodules are typically seen 10 years or more after treatment. Risk increases with the amount of radiation received to the area.
Symptoms/When to Call
Symptoms of hypothyroidism (the most common complication) are a result of the thyroid not making enough of the hormones. These include:
- Weight gain
- Dry skin and brittle hair
- Always feeling cold
- Mood changes or feeling sad or depressed
Symptoms of hyperthyroidism are a result of the thyroid making too much of the hormones. These include:
- Feeling anxious or agitated
- Problems concentrating
- Fast heart rate
- Sweating or feeling hot all the time
- Weight loss
- Bulging eyes
Thyroid nodules can appear as a painless bump or lump in your neck. Depending on the location, you may be able to feel it or it can press on your throat, causing symptoms such as difficulty swallowing or a change in your voice. Many thyroid nodules will have no noticeable symptoms.
Prevention and Treatment
Survivors who have had radiation to the brain or neck and/or symptoms of hypothyroidism should have thyroid function tests (blood tests, such as a TSH) checked. If someone is found to be hypothyroid, they are started on thyroid hormone replacement and blood tests are monitored to ensure the correct level of medication over time.
In addition, anyone who received radiation to the neck area should have their thyroid gland examined for any nodules. Your primary care provider would do this by feeling the thyroid gland during your annual physical exam. Any concerns on physical exam would prompt further evaluation with a thyroid ultrasound, which can help understand if the nodules are benign (not cancerous) or concerning (possibly cancerous). If the nodules look concerning, a biopsy (FNA or fine needle aspiration) is performed. The good news is thyroid cancer is often curable. Cancers found early can be often be treated with removal of the thyroid gland.