Role of Nuclear Medicine in Thyroid Disorders

Thyroid disorders affect millions worldwide, from common conditions like hyperthyroidism and hypothyroidism to complex issues like thyroid nodules and thyroid cancer. Accurate diagnosis and effective treatment are critical for managing these disorders, and this is where nuclear medicine becomes invaluable. Nuclear medicine not only helps in detailed imaging of thyroid function and structure but also offers targeted therapies that directly treat thyroid diseases. In major Indian cities such as Delhi, Mumbai, and Bengaluru, nuclear medicine has become a cornerstone in thyroid care, making early detection and precise treatment widely accessible.

What is nuclear medicine?

Nuclear medicine is a medical specialty that uses small amounts of radioactive materials (radiotracers) to diagnose, monitor, and treat diseases. In thyroid disorders, it primarily involves:

• Radioactive iodine (I-123 or I-131) for imaging and therapy.
• Gamma cameras and SPECT scans for visualizing the thyroid gland.
• Targeted radionuclide therapy to manage overactive thyroid or destroy cancerous cells.

The combination of functional imaging and therapy makes nuclear medicine uniquely suited for thyroid conditions.

Why is nuclear medicine important in thyroid disorders?

The thyroid gland regulates metabolism, energy production, and many bodily functions. Disorders in this gland can have widespread effects. Nuclear medicine helps by:

• Offering precise functional imaging rather than just anatomical details.
• Identifying overactive or underactive thyroid tissue.
• Detecting thyroid nodules and assessing their activity.
• Treating conditions like hyperthyroidism and certain types of thyroid cancer.
• Monitoring treatment effectiveness and recurrence.

Common thyroid disorders evaluated or treated with nuclear medicine

Nuclear medicine plays a significant role in managing:

• Hyperthyroidism: Overactive thyroid producing excess hormones.
• Hypothyroidism: Underactive thyroid, though less frequently diagnosed directly with nuclear medicine.
• Thyroid nodules: Single or multiple lumps that may be benign or malignant.
• Thyroid cancer: Including papillary, follicular, and metastatic cases.
• Goiter: Enlarged thyroid gland, sometimes due to autoimmune disease.

Nuclear medicine tests for thyroid disorders

1. Thyroid scan

A thyroid scan is a functional imaging test that shows the size, shape, and activity of the thyroid gland.

• A small dose of radioactive iodine (I-123) or technetium-99m is administered orally or intravenously.
• The thyroid naturally absorbs iodine; the radiotracer collects in active thyroid tissue.
• Using a gamma camera, detailed images reveal:
  • “Hot” nodules: Overactive, usually benign.
  • “Cold” nodules: Underactive, could be benign or malignant.
  • Diffuse uptake: Seen in conditions like Graves’ disease.
  • Patchy uptake: Seen in thyroiditis.

2. Radioactive iodine uptake (RAIU) test

This test measures how much radioactive iodine the thyroid absorbs over a period (usually 6 and 24 hours).

• Higher uptake suggests hyperthyroidism (e.g., Graves’ disease).
• Lower uptake may indicate thyroiditis or other causes.

RAIU is often combined with a thyroid scan for a complete assessment.

Nuclear medicine therapies for thyroid disorders

1. Radioiodine therapy for hyperthyroidism

For conditions like Graves’ disease, toxic multinodular goiter, or toxic adenoma:

• Patients receive a therapeutic dose of radioactive iodine (I-131) orally.
• The iodine accumulates in overactive thyroid tissue.
• Radiation destroys excess thyroid tissue, reducing hormone production.

Advantages:

• Non-surgical, outpatient treatment.
• High success rate in resolving hyperthyroidism.
• Generally safe with manageable side effects.

2. Radioiodine therapy for thyroid cancer

After thyroidectomy (surgical removal of the thyroid), residual thyroid tissue or microscopic cancer cells may remain.

• High-dose I-131 therapy targets and destroys these remaining cells.
• Helps reduce recurrence risk and treat distant metastases.

This targeted therapy is a key reason for improved survival rates in thyroid cancer patients.

3. Whole-body radioiodine scan

Used post-treatment to check for:

• Remaining thyroid tissue.
• Recurrent or metastatic thyroid cancer.
• Effectiveness of previous radioiodine therapy.

Advantages of nuclear medicine in thyroid care

• Functional imaging: Reveals how thyroid tissue behaves, not just how it looks.
• Targeted therapy: Radioiodine selectively affects thyroid tissue, sparing other organs.
• Non-invasive: Most procedures are painless and performed as outpatient services.
• Monitoring: Enables long-term tracking of disease recurrence or progression.

These features help doctors design personalized, effective treatment plans.

Limitations and precautions

Like all medical procedures, nuclear medicine in thyroid disorders has some considerations:

• Radiation exposure: Though low, it may not be suitable during pregnancy or breastfeeding.
• Delayed effect: Radioiodine therapy may take weeks to months to fully control hyperthyroidism.
• Hypothyroidism risk: Post-treatment, some patients may require lifelong thyroid hormone replacement.
• False positives/negatives: Inflammation or certain medications can alter scan results.

Doctors assess each patient’s risk factors and explain these before proceeding.

How to prepare for a nuclear medicine thyroid test or treatment

• Avoid iodine-rich foods or contrast agents: These can interfere with uptake.
• Inform your doctor about pregnancy or breastfeeding: To evaluate safety.
• Stop certain medications temporarily: Such as antithyroid drugs or supplements containing iodine.
• Wear comfortable clothes and remove metal jewelry: To improve scan clarity.
• Follow fasting instructions if advised: Based on the specific procedure.

Nuclear medicine in India

Across major cities like Delhi, Mumbai, Chennai, and Bengaluru:

• Nuclear medicine centers are expanding.
• NABH- and NABL-accredited facilities ensure safety and quality.
• Advanced imaging tools like SPECT/CT and PET/CT enhance diagnostic accuracy.
• Experienced nuclear medicine physicians offer personalized care.

Conclusion

Nuclear medicine has transformed the way thyroid disorders are diagnosed and treated. From detailed functional scans to targeted radioiodine therapy, these tools help doctors detect disease early, design effective treatments, and monitor outcomes precisely. Whether managing hyperthyroidism, evaluating thyroid nodules, or treating thyroid cancer, nuclear medicine remains at the heart of modern thyroid care. As awareness and technology continue to improve patients in India and worldwide have more opportunities for safe, accurate, and life-changing treatment.

Frequently Asked Questions (FAQ’s)

What is a thyroid scan?

A thyroid scan uses a small dose of radioactive material to create images showing the thyroid gland’s shape, size, and activity.

What is radioiodine therapy?

A treatment where radioactive iodine (I-131) destroys overactive or cancerous thyroid tissue.

Is nuclear medicine safe for thyroid disorders?

Yes, it uses very small doses of radiation, carefully controlled to minimize risk.

Can nuclear medicine treat thyroid nodules?

It can help assess nodules and treat “hot” nodules causing hyperthyroidism.

Will I become hypothyroid after treatment?

Some patients may develop hypothyroidism and need lifelong thyroid hormone pills.

How long does a thyroid scan take?

Usually around 30–60 minutes, depending on the procedure.

Is nuclear medicine used for thyroid cancer?

Yes, radioiodine therapy targets and destroys residual thyroid tissue or cancer cells after surgery.

Do I need to stop medications before a scan?

Sometimes, especially antithyroid drugs or iodine supplements follow your doctor’s advice.

Can pregnant women undergo nuclear medicine tests?

Generally not, due to the risk of radiation exposure to the fetus.

Is nuclear medicine widely available in India?

Yes, especially in major cities like Delhi, Mumbai, and Bengaluru, with modern, accredited centers.