A regimen of radioactive iodine I-131 is a common treatment for an overactive thyroid gland (hyperthyroidism) and for thyroid cancer. The treatment is a single dose swallowed in liquid, capsule or pill form. It is very effective, and side effects are uncommon.
The thyroid gland accumulates iodine from foods such as fish and iodized salt, and uses it to produce thyroid hormone necessary for body function. Radioactive iodine is designed to disrupt function of thyroid cells, resulting in reduced thyroid hormone production.
Primary Side Effect
Typically the I-131 radioactive iodine pill destroys so much of the thyroid gland that the patient needs to take daily thyroid pills for the rest of his life. This is the primary and most common side effect.
Throat and Neck Effects
Some people develop a sore throat or neck tenderness a few days after treatment. Acetaminophen or a non-steroidal anti-inflammatory drug such as ibuprofen can relieve this pain. Less commonly, more severe neck discomfort lasts for a few weeks.
Patients may experience nausea for a few hours after taking the iodine pill. Doctors advise not eating for at least two hours before taking it.
Considerations for Women
Women who are breastfeeding must stop doing so before taking the iodine pill. Pregnant women should not receive this treatment because it can harm the developing baby.
Patients should take precautions to not expose other people and pets to radioactivity. They should not sit closely to other people for prolonged periods of time or share food, utensils and drinking glasses for a few days.