I-131 Radioiodine therapy (10 mCi) for Hyperthyroidism

Overview

I-131 Radioiodine Therapy (10 mCi) is a widely accepted and effective treatment for hyperthyroidism, particularly in conditions such as Graves’ disease, toxic multinodular goitre, and solitary hyperfunctioning thyroid nodules. This form of therapy uses the thyroid gland’s natural ability to absorb iodine to selectively destroy overactive thyroid tissues. Administered as a small oral dose, 10 millicurie (mCi) of Iodine-131 (I-131) is considered a low-dose therapy, usually provided on an outpatient basis, and is highly successful in restoring normal thyroid hormone levels.  Radioiodine therapy has been in clinical use for decades and is endorsed by major medical bodies as a first-line treatment for hyperthyroidism in suitable candidates. This therapy is non-invasive, painless, and offers a permanent solution for patients who either do not respond well to anti-thyroid medications or experience recurrent symptoms.

What is I-131 Radioiodine Therapy for Hyperthyroidism?

I-131 Radioiodine therapy works by using a radioactive isotope of iodine—Iodine-131—that is absorbed naturally by thyroid tissues. Once inside the thyroid, the radioiodine emits beta radiation, which gradually destroys the overactive or enlarged thyroid cells. Unlike surgery or lifelong use of anti-thyroid medications, I-131 therapy provides a targeted and long-term solution, effectively reducing hormone production to normal or low levels. This helps manage the symptoms of hyperthyroidism while minimizing long-term medication dependency or complications.

Indications for I-131 Therapy (10 mCi)

The 10 mCi dose is typically used in mild to moderate hyperthyroid cases and may include the following conditions:

• Graves’ Disease
  An autoimmune disorder where antibodies stimulate the thyroid to produce excess hormones.
• Toxic Multinodular Goitre
  Multiple nodules in the thyroid gland that produce thyroid hormone independently, leading to excess levels.
• Solitary Hyperfunctioning Nodule (Toxic Adenoma)
  A single thyroid nodule that autonomously produces thyroid hormone, leading to suppressed normal tissue.
• Recurrent Hyperthyroidism After Surgery or Medications
  Cases where the disease has returned after initial treatment.
• Nontoxic Multinodular Goitre (for reduction of size)
  While not hyperfunctioning, large goitres may be treated for symptomatic relief such as compressive symptoms or cosmetic concerns.

How Does the Treatment Work?

1. Oral Administration
   • The therapy is given as a single oral dose (capsule or liquid).
   • No hospitalization is typically required for a 10 mCi dose.
2. Targeted Action
   • The radioactive iodine is absorbed by thyroid cells only.
   • Beta radiation damages the overactive or enlarged tissues over a few weeks to months.
3. Gradual Reduction in Function
   • Hormone production declines steadily, leading to euthyroid (normal) or hypothyroid states.
   • In cases of hypothyroidism, thyroid hormone replacement (levothyroxine) is prescribed.

Preparation for I-131 Radioiodine Therapy

To maximize the therapy’s effectiveness, proper preparation is important:

Discontinue Anti-thyroid Medications

Patients are often advised to stop medications like carbimazole, methimazole, or propylthiouracil 3–7 days before treatment. This helps enhance the uptake of radioactive iodine by the thyroid tissue.

Low-Iodine Diet

A low-iodine diet for 1–2 weeks prior may be recommended to improve iodine uptake. This includes avoiding:

• Iodized salt
• Dairy products
• Seafood
• Soy products
• Processed foods with food coloring

Blood Tests and Thyroid Scan

Baseline tests such as:

• Thyroid function tests (TSH, T3, T4)
• Thyroid uptake scan (optional)
• CBC, liver and renal profile if medically necessary

These assessments help determine if the patient is fit for therapy and the appropriate dosing.

Post-Treatment Instructions

After receiving the radioiodine capsule:

• Avoid close contact with children and pregnant women for 3–5 days
• Maintain distance from family members (especially at night)
• Sleep separately and use separate utensils and toilet if possible
• Flush toilet twice after each use
• Hydrate well to flush the radioactive iodine from the body
• Resume anti-thyroid medications only if directed by the doctor

These radiation safety precautions are short-term and designed to protect others from minimal radiation exposure.

What to Expect After the Therapy

Patients will not experience any immediate change, as the destruction of thyroid tissue is gradual, taking several weeks to a few months. During this period:

• Symptoms of hyperthyroidism (e.g., tremors, palpitations, weight loss) will gradually subside
• Follow-up blood tests will assess thyroid function
• Some patients may become hypothyroid, needing lifelong levothyroxine supplementation
• Regular monitoring is required until stable thyroid hormone levels are achieved

Most patients see complete resolution of symptoms with one dose. Occasionally, a second dose may be required if the first is insufficient.

Benefits of I-131 Therapy (10 mCi)

• Permanent solution for hyperthyroidism
• Non-surgical and minimally invasive
• No need for long-term anti-thyroid medications
• High success rate (especially in Graves’ disease and toxic nodules)
• Minimal side effects
• Cost-effective and outpatient-friendly

Risks and Side Effects

Like all treatments, radioiodine therapy comes with potential risks:

• Hypothyroidism (common and treatable with medication)
• Mild neck pain or swelling
• Sore throat in some cases
• Temporary worsening of eye symptoms in Graves’ disease
• Contraindicated in pregnancy and breastfeeding

Your doctor will explain any possible side effects and help you manage them proactively.

Who Should Not Receive I-131 Therapy?

• Pregnant or breastfeeding women
• Patients with severe uncontrolled thyroid eye disease (unless co-treated with steroids)
• Those who have recently received iodinated contrast (CT scan)

Follow-Up and Monitoring

Post-therapy monitoring includes:

• Thyroid function tests at 4, 8, and 12 weeks
• Regular checks for signs of hypothyroidism
• Starting levothyroxine therapy if TSH rises above normal
• Long-term monitoring of hormone levels and symptom control

Conclusion

I-131 Radioiodine Therapy (10 mCi) is a safe, proven, and effective solution for managing various types of hyperthyroidism, including Graves’ disease, toxic nodular goitre, and autonomously functioning nodules. It provides long-term control by selectively destroying overactive thyroid tissue and reducing excessive hormone production. With minimal discomfort, high success rates, and limited complications, it remains a first-line therapy in many clinical scenarios. Patients who are well-prepared and closely monitored can expect excellent outcomes and return to a symptom-free, stable hormonal state with minimal disruption to their lives. For personalized recommendations, please consult your endocrinologist or nuclear medicine specialist.