Thyroid Cancer
Most common in younger women. Papillary, follicular, and other types explained — staging, treatment, and living well after diagnosis.
Thyroid Cancer at a Glance
Key facts you should know right away. These numbers represent global averages — your individual situation may differ.
Thyroid cancer is one of the most treatable cancers. The overwhelming majority of people diagnosed with the most common types — papillary and follicular — have excellent long-term outcomes. The rising incidence of thyroid cancer over the past several decades is due in large part to improved detection through ultrasound and imaging, which identifies small cancers that previously went unnoticed. This does not mean thyroid cancer is becoming more dangerous; it means we are finding it earlier.
That said, some types — particularly anaplastic thyroid cancer — are aggressive and require urgent, specialized treatment. Understanding your specific type, stage, and molecular profile is essential for getting the right care.
What Is Thyroid Cancer?
The Thyroid Gland
The thyroid is a small, butterfly-shaped gland located at the base of your neck, just below the Adam's apple. Despite its small size — typically weighing only 15 to 20 grams — this gland plays a critical role in your body's daily function.
The thyroid produces two main hormones: T3 (triiodothyronine) and T4 (thyroxine). These hormones regulate your metabolism, controlling how fast your body burns calories, how quickly your heart beats, your body temperature, and how your muscles and organs function. The thyroid also produces calcitonin, a hormone involved in calcium and bone metabolism.
The thyroid is controlled by the pituitary gland in your brain, which releases thyroid-stimulating hormone (TSH). When thyroid hormone levels are low, TSH goes up to signal the thyroid to produce more. When levels are adequate, TSH goes down. This feedback loop is important to understand because it becomes central to treatment and monitoring after thyroid cancer diagnosis.
How Thyroid Cancer Develops
Thyroid cancer occurs when cells in the thyroid gland develop mutations in their DNA that cause them to grow and multiply in an uncontrolled manner. These abnormal cells can form a tumor and, in some cases, spread to nearby lymph nodes or distant organs.
Most thyroid cancers arise from follicular cells — the cells that produce T3 and T4 hormones. These are called differentiated thyroid cancers (papillary and follicular types), and they tend to retain some of the characteristics of normal thyroid cells, including the ability to absorb iodine. This is important because it makes them treatable with radioactive iodine therapy.
A smaller percentage of thyroid cancers arise from C cells (also called parafollicular cells), which produce calcitonin. These are called medullary thyroid cancers and behave differently from differentiated types.
In rare cases, thyroid cancer cells lose all resemblance to normal thyroid tissue. This is anaplastic thyroid cancer, one of the most aggressive cancers in the human body.
Types of Thyroid Cancer
Not all thyroid cancers are the same. The type determines treatment approach, monitoring strategy, and long-term outlook.
Papillary Thyroid Cancer (~80%)
The most common type, accounting for approximately 80% of all thyroid cancers. Papillary thyroid cancer (PTC) usually grows slowly and typically develops in one lobe of the thyroid. It is most common in women between the ages of 30 and 50. PTC often spreads to lymph nodes in the neck, but even when it does, the long-term prognosis remains excellent. The 5-year survival rate for localized papillary thyroid cancer exceeds 98%. This type responds well to surgery and radioactive iodine therapy. Common molecular alterations include the BRAF V600E mutation and RET/PTC rearrangements.
Follicular Thyroid Cancer (~10–15%)
The second most common type, accounting for 10 to 15% of cases. Follicular thyroid cancer (FTC) also arises from follicular cells and tends to grow slowly. Unlike papillary cancer, it less commonly spreads to lymph nodes but is more likely to spread through the bloodstream to distant sites, such as the lungs and bones. FTC cannot be definitively diagnosed by fine-needle aspiration alone — surgery is often required to distinguish it from a benign follicular adenoma. It also responds to surgery and radioactive iodine. RAS mutations are the most common molecular alteration.
Hürthle Cell Carcinoma
Previously classified as a variant of follicular thyroid cancer, Hürthle cell (oncocytic) carcinoma is now recognized as a distinct entity by the WHO. It accounts for approximately 3 to 5% of thyroid cancers. Hürthle cell carcinoma is generally considered more aggressive than standard follicular cancer. It is less likely to absorb iodine, which can make radioactive iodine therapy less effective. Treatment typically involves total thyroidectomy, and close follow-up is important due to a higher risk of recurrence compared to papillary and follicular types.
Medullary Thyroid Cancer (~4%)
Medullary thyroid cancer (MTC) arises from the C cells that produce calcitonin. It accounts for approximately 4% of thyroid cancers. About 25% of MTC cases are hereditary, caused by mutations in the RET proto-oncogene and often part of a syndrome called Multiple Endocrine Neoplasia type 2 (MEN2). The remaining 75% are sporadic (not inherited). MTC does not respond to radioactive iodine therapy because C cells do not absorb iodine. Calcitonin and CEA (carcinoembryonic antigen) are used as tumor markers. Genetic testing for RET mutations is recommended for all MTC patients, as results affect both the patient and their family members.
Anaplastic Thyroid Cancer (~1–2%)
The rarest and most aggressive form of thyroid cancer, accounting for only 1 to 2% of cases. Anaplastic (undifferentiated) thyroid cancer grows very rapidly and is difficult to treat. It is most common in adults over age 60. Because the cells have lost all resemblance to normal thyroid tissue, they do not absorb iodine and do not respond to radioactive iodine. Anaplastic thyroid cancer is always classified as Stage IV at diagnosis, regardless of tumor size or spread. Treatment typically involves a combination of surgery (when possible), external beam radiation, and chemotherapy. BRAF-targeted therapies (dabrafenib + trametinib) have shown promise for BRAF-mutated anaplastic cases. Despite its severity, advances in targeted therapy are improving outcomes for some patients.
What Increases Thyroid Cancer Risk?
Having a risk factor does not mean you will develop thyroid cancer. Many people with risk factors never develop the disease, and some people diagnosed have no known risk factors.
Symptoms of Thyroid Cancer
Early thyroid cancer often causes no symptoms at all. It is frequently discovered incidentally during imaging for other conditions or during a routine physical exam.
When symptoms do occur, they may include:
- A lump or nodule in the neck — The most common sign. You or your doctor may feel a lump in the front of your neck, near the thyroid. Not all lumps are visible, but some can be seen or felt through the skin.
- Swollen lymph nodes in the neck — Enlarged lymph nodes may indicate that thyroid cancer has spread to the lymphatic system. This is particularly common in papillary thyroid cancer.
- Hoarseness or voice changes — The recurrent laryngeal nerve, which controls your vocal cords, runs right next to the thyroid. A growing tumor can press on this nerve and cause persistent hoarseness.
- Difficulty swallowing (dysphagia) — A large thyroid nodule or tumor can press on the esophagus, making it harder to swallow food or liquids.
- Difficulty breathing — In rare cases, a tumor can press on the trachea (windpipe), causing a feeling of shortness of breath or airway obstruction.
- Pain in the neck or throat — While most thyroid cancers are painless, some patients experience pain in the front of the neck that may radiate to the ears.
How Thyroid Cancer Is Diagnosed
Diagnosis typically involves several steps, from physical examination to molecular testing. Here is what to expect.
Physical Examination
Your doctor will feel (palpate) your neck to check for lumps, nodules, or enlargement of the thyroid or nearby lymph nodes. They will also ask about symptoms such as hoarseness, difficulty swallowing, and any family history of thyroid disease or cancer.
Thyroid Ultrasound
Ultrasound is the primary imaging tool for evaluating thyroid nodules. It uses sound waves to create detailed images of the thyroid gland and can determine the size, composition (solid vs. cystic), and characteristics of a nodule. Features that raise concern for cancer include irregular margins, microcalcifications (tiny calcium deposits), a taller-than-wide shape, and increased blood flow within the nodule. Ultrasound is also used to evaluate cervical (neck) lymph nodes for signs of spread.
The ACR TI-RADS (Thyroid Imaging Reporting and Data System) is a standardized scoring system used by radiologists to classify thyroid nodules based on their ultrasound appearance and recommend whether a biopsy is needed.
Fine-Needle Aspiration (FNA) Biopsy
If a nodule has suspicious features on ultrasound, a fine-needle aspiration biopsy is performed. A thin needle is inserted into the nodule (usually guided by ultrasound) to extract a sample of cells. These cells are examined under a microscope by a pathologist. FNA is the single most important tool for determining whether a thyroid nodule is benign or malignant.
The Bethesda System (FNA Results)
FNA results are classified using the Bethesda System for Reporting Thyroid Cytopathology, which has six categories:
- Bethesda I — Nondiagnostic / Unsatisfactory: The sample did not contain enough cells for evaluation. A repeat FNA is usually recommended.
- Bethesda II — Benign: The cells are normal. Risk of malignancy is approximately 0 to 3%. Routine follow-up with ultrasound is typically recommended.
- Bethesda III — Atypia of Undetermined Significance (AUS) / Follicular Lesion of Undetermined Significance (FLUS): Some abnormal cells are present, but they do not clearly indicate cancer. Risk of malignancy is approximately 6 to 18%. Molecular testing or repeat FNA may be recommended.
- Bethesda IV — Follicular Neoplasm / Suspicious for Follicular Neoplasm: Cells suggest a follicular growth pattern. Risk of malignancy is approximately 10 to 40%. Surgery (usually a diagnostic lobectomy) is often recommended because FNA alone cannot distinguish between a benign follicular adenoma and follicular carcinoma.
- Bethesda V — Suspicious for Malignancy: Cells strongly suggest cancer but do not definitively confirm it. Risk of malignancy is approximately 45 to 75%. Surgery is typically recommended.
- Bethesda VI — Malignant: The cells confirm cancer (most often papillary thyroid cancer). Risk of malignancy is 94 to 99%. Surgery is planned.
Molecular Testing for Indeterminate Nodules
When FNA results are indeterminate (Bethesda III or IV), molecular testing can help determine the likelihood of malignancy without requiring surgery. Two widely used tests include:
- Afirma Gene Sequencing Classifier (GSC): A genomic test that analyzes gene expression patterns. If the result is "benign," the nodule can often be monitored rather than surgically removed.
- ThyroSeq v3: A next-generation sequencing panel that tests for mutations and gene fusions in over 112 genes associated with thyroid cancer. A negative result is associated with a very low risk of malignancy.
These tests have significantly reduced the number of unnecessary diagnostic surgeries for patients with indeterminate thyroid nodules.
Blood Tests
Blood tests are an important part of evaluation:
- TSH (thyroid-stimulating hormone): Measures overall thyroid function. A low TSH may indicate a hyperfunctioning ("hot") nodule, which is rarely cancerous. An elevated TSH may be associated with a higher risk of malignancy in a nodule.
- Thyroglobulin (Tg): A protein made by follicular thyroid cells. While not useful for initial diagnosis, thyroglobulin becomes an essential tumor marker after treatment for differentiated thyroid cancer. Rising thyroglobulin levels after surgery may indicate recurrence.
- Calcitonin: Produced by C cells. Elevated calcitonin levels may indicate medullary thyroid cancer and should prompt further investigation. This test is particularly important if MTC is suspected.
- CEA (carcinoembryonic antigen): Used alongside calcitonin as a tumor marker for medullary thyroid cancer.
Thyroid Cancer Staging (TNM)
Staging describes how far the cancer has spread and is critical for treatment planning. Thyroid cancer staging has unique features compared to other cancers.
Important: Age Matters in Thyroid Cancer Staging
Thyroid cancer staging is unlike almost any other cancer because age at diagnosis is a factor in the staging system. For differentiated thyroid cancer (papillary and follicular), patients under 55 years old at diagnosis can only be classified as Stage I or Stage II, regardless of tumor size or lymph node involvement. This reflects the fact that younger patients have an excellent prognosis even with more advanced disease.
TNM for Differentiated Thyroid Cancer (Papillary & Follicular)
Patients Under 55 Years Old
- Stage I: Any size tumor, may have spread to lymph nodes, but has NOT spread to distant sites.
- Stage II: Any size tumor that HAS spread to distant sites (lungs, bones, etc.).
Patients 55 Years Old and Older
- Stage I: Tumor 4 cm or smaller, confined to the thyroid, no lymph node involvement, no distant spread.
- Stage II: Tumor larger than 4 cm but confined to the thyroid, OR any size tumor with minimal spread beyond the thyroid to nearby muscles. No distant spread.
- Stage III: Tumor has grown into nearby structures in the neck (such as the subcutaneous tissue, larynx, trachea, esophagus, or recurrent laryngeal nerve), OR any tumor with lymph node involvement.
- Stage IV: Tumor has invaded major structures (such as the spine, large blood vessels, or prevertebral fascia) OR has spread to distant organs.
Staging for Medullary Thyroid Cancer
Medullary thyroid cancer uses a standard TNM staging system that does not incorporate age as a factor:
- Stage I: Small tumor (2 cm or less), confined to the thyroid.
- Stage II: Tumor larger than 2 cm but confined to the thyroid, or has grown minimally beyond the thyroid.
- Stage III: Spread to neck lymph nodes.
- Stage IV: Spread to nearby structures or distant organs.
Staging for Anaplastic Thyroid Cancer
All anaplastic thyroid cancers are automatically classified as Stage IV at diagnosis:
- Stage IVA: Tumor confined to the thyroid (potentially resectable).
- Stage IVB: Tumor has invaded beyond the thyroid into nearby structures.
- Stage IVC: Distant metastasis (spread to lungs, bones, or other distant sites).
Biomarkers & Molecular Testing
Molecular profiling of thyroid cancer is increasingly important for diagnosis, treatment decisions, and predicting prognosis.
Key Molecular Markers
BRAF V600E Mutation
The most common genetic alteration in papillary thyroid cancer, found in approximately 40 to 60% of cases. BRAF V600E is associated with more aggressive tumor behavior, including higher rates of lymph node spread, extrathyroidal extension, and resistance to radioactive iodine. However, its presence alone does not determine prognosis — other factors must be considered. In anaplastic thyroid cancer, the BRAF V600E mutation is important because it makes the cancer potentially responsive to BRAF-targeted therapies (dabrafenib + trametinib).
RAS Mutations
RAS mutations (NRAS, HRAS, KRAS) are the most common alterations in follicular thyroid cancer and are also found in follicular variant papillary thyroid cancer. They are generally associated with a lower-risk cancer phenotype compared to BRAF V600E.
RET/PTC Rearrangements
Gene fusions involving the RET proto-oncogene are found in a subset of papillary thyroid cancers, particularly in patients with a history of radiation exposure and in younger patients. These rearrangements are important for targeted therapy eligibility.
RET Point Mutations (Medullary Thyroid Cancer)
Activating mutations in the RET gene drive medullary thyroid cancer. Approximately 25% of MTC cases are hereditary (germline RET mutations), and additional sporadic cases have somatic RET mutations. Selpercatinib and pralsetinib are RET-targeted therapies approved for RET-mutated medullary thyroid cancer and have shown significant response rates.
TERT Promoter Mutations
Mutations in the TERT (telomerase reverse transcriptase) promoter are associated with more aggressive thyroid cancers and a worse prognosis. The combination of BRAF V600E plus a TERT promoter mutation is associated with the highest-risk differentiated thyroid cancers, including higher rates of recurrence and cancer-related mortality.
Molecular Classifiers for Indeterminate Nodules
As described in the diagnosis section, molecular tests such as Afirma GSC and ThyroSeq v3 are used to evaluate indeterminate FNA results (Bethesda III/IV). These tests analyze genetic alterations to estimate the probability that a nodule is cancerous, helping to guide decisions about whether to proceed with surgery or continue observation.
Thyroid Cancer Treatment
Treatment depends on the type, stage, and molecular characteristics of your cancer. Here is a comprehensive overview of the major treatment approaches.
Surgery
Surgery is the primary treatment for nearly all thyroid cancers. The two main surgical options are:
- Lobectomy (hemilobectomy): Removal of one lobe of the thyroid. This may be sufficient for small (under 4 cm), low-risk papillary thyroid cancers confined to one lobe without lymph node involvement. An advantage of lobectomy is that many patients retain enough thyroid function to avoid lifelong thyroid hormone replacement, though some may still require it.
- Total thyroidectomy: Removal of the entire thyroid gland. Recommended for larger tumors, tumors in both lobes, tumors with aggressive features, when radioactive iodine therapy is planned, and for medullary and anaplastic thyroid cancers. After total thyroidectomy, lifelong thyroid hormone replacement (levothyroxine) is required.
Lymph node dissection may also be performed if cancer has spread to nearby lymph nodes. Central compartment dissection (nodes around the thyroid) and lateral neck dissection (nodes along the side of the neck) are the most common types.
The choice between lobectomy and total thyroidectomy should be discussed thoroughly with your surgeon. Factors include tumor size, type, molecular markers, lymph node involvement, patient preference, and whether RAI therapy will be needed.
Radioactive Iodine (RAI) Therapy
Radioactive iodine (I-131) therapy takes advantage of the fact that thyroid cells — including most differentiated thyroid cancer cells — absorb iodine. After total thyroidectomy, any remaining thyroid tissue (including microscopic cancer cells) will absorb the radioactive iodine and be destroyed.
RAI is typically recommended for:
- Intermediate- and high-risk differentiated thyroid cancers
- Cancers that have spread to lymph nodes or beyond the thyroid
- Cancers with aggressive features (vascular invasion, extrathyroidal extension)
RAI is generally not recommended for very low-risk papillary microcarcinomas (tumors under 1 cm without aggressive features). It is not effective for medullary or anaplastic thyroid cancer.
Before RAI, patients must either stop taking thyroid hormone medication for several weeks (to raise TSH levels) or receive injections of recombinant human TSH (Thyrogen). A low-iodine diet is typically followed for 1 to 2 weeks before treatment to help the body absorb the radioactive iodine more effectively.
After RAI, a whole-body scan is performed to see where the radioactive iodine was absorbed, which helps identify any remaining thyroid tissue or cancer.
TSH Suppression Therapy
After surgery for differentiated thyroid cancer, all patients require thyroid hormone replacement. However, for cancer patients, the goal is often more than just replacing normal hormone levels. TSH suppression therapy involves taking a slightly higher dose of levothyroxine to keep TSH levels low — because TSH can stimulate the growth of any remaining thyroid cancer cells.
The degree of TSH suppression depends on the patient's risk level:
- High-risk patients: TSH is suppressed to below 0.1 mIU/L
- Intermediate-risk patients: TSH is maintained between 0.1 and 0.5 mIU/L
- Low-risk patients with no evidence of disease: TSH can be maintained in the low-normal range (0.5 to 2.0 mIU/L)
Over-suppression of TSH carries risks, including bone loss (osteoporosis), irregular heartbeat (atrial fibrillation), and anxiety. Your endocrinologist will carefully balance cancer risk against the risks of excessive suppression.
External Beam Radiation Therapy
Unlike radioactive iodine (which is taken internally), external beam radiation delivers targeted radiation from a machine outside the body. It is not a standard treatment for most thyroid cancers but plays an important role in specific situations:
- Anaplastic thyroid cancer: External radiation is a key part of treatment, often combined with chemotherapy.
- Medullary thyroid cancer: May be used after surgery for locally advanced disease.
- Differentiated thyroid cancer: May be used when RAI is no longer effective (RAI-refractory disease) or when there is residual disease after surgery that cannot be removed.
Targeted Therapy & Systemic Treatment
For advanced thyroid cancers that do not respond to surgery and RAI, several targeted therapies are available:
- Lenvatinib (Lenvima): A multi-kinase inhibitor approved for progressive, RAI-refractory differentiated thyroid cancer. It targets VEGF receptors and other pathways involved in tumor growth and blood supply.
- Sorafenib (Nexavar): Another multi-kinase inhibitor approved for RAI-refractory differentiated thyroid cancer. It was the first targeted therapy approved for this indication.
- Selpercatinib (Retevmo): A highly selective RET inhibitor approved for RET-mutated medullary thyroid cancer and RET fusion-positive thyroid cancers. It has shown high response rates and a manageable side-effect profile.
- Pralsetinib (Gavreto): Another selective RET inhibitor approved for RET-altered thyroid cancers.
- Cabozantinib (Cometriq): Approved for progressive medullary thyroid cancer. Targets MET, VEGFR2, and RET.
- Vandetanib (Caprelsa): Approved for advanced medullary thyroid cancer. Targets RET, VEGFR, and EGFR.
- Dabrafenib + Trametinib: A BRAF/MEK inhibitor combination that has shown significant activity in BRAF V600E-mutated anaplastic thyroid cancer and is approved for this indication.
Clinical trials continue to explore new combinations and novel agents, particularly immunotherapy approaches. If you have advanced thyroid cancer, ask your oncologist about clinical trial eligibility.
Active Surveillance
For very small (under 1 cm), low-risk papillary microcarcinomas without evidence of lymph node involvement, extrathyroidal extension, or aggressive molecular features, active surveillance (watchful waiting) may be an appropriate alternative to immediate surgery.
This approach was pioneered at Kuma Hospital in Japan, where studies following patients for over 10 years showed that the vast majority of these small cancers did not grow or spread. Active surveillance involves regular ultrasound monitoring (typically every 6 to 12 months) and delaying surgery unless the tumor grows beyond 1 cm, spreads to lymph nodes, or the patient prefers surgery.
Active surveillance is gaining acceptance in the United States, Europe, and elsewhere as a way to avoid the side effects of surgery and lifelong hormone replacement for cancers that may never become clinically significant. The 2015 ATA guidelines support active surveillance as an alternative to surgery for appropriately selected patients.
Life After Thyroid Cancer
Surviving thyroid cancer comes with its own long-term challenges. Your body is different now, and that deserves recognition and support.
Lifelong Thyroid Hormone Replacement
After total thyroidectomy, you will need to take levothyroxine every day for the rest of your life. This medication replaces the hormones your thyroid used to produce. Finding the right dose can take time and requires regular blood tests to monitor TSH, free T4, and sometimes free T3 levels. Even small changes in dosage can significantly affect how you feel.
Tips for managing thyroid hormone replacement:
- Take your levothyroxine on an empty stomach, at least 30 to 60 minutes before eating or drinking (other than water).
- Avoid taking it with calcium, iron supplements, or antacids, which can interfere with absorption.
- Be consistent about the brand or formulation you use — switching between brands can alter absorption.
- Report symptoms of over-replacement (anxiety, rapid heartbeat, insomnia, weight loss) or under-replacement (fatigue, weight gain, depression, cold intolerance) to your doctor.
Monitoring and Follow-Up
After treatment for differentiated thyroid cancer, long-term monitoring is essential:
- Thyroglobulin (Tg) levels: After total thyroidectomy and RAI, thyroglobulin should be undetectable or very low. Rising levels may indicate recurrence. Anti-thyroglobulin antibodies (TgAb) can interfere with this test, so they are monitored as well.
- Neck ultrasound: Regular ultrasound examinations of the neck to check for any recurrence in the thyroid bed or cervical lymph nodes. Frequency depends on your risk level — typically every 6 to 12 months initially, then annually or less frequently if you remain disease-free.
- Whole-body scans: Diagnostic whole-body iodine scans may be performed periodically for intermediate- and high-risk patients.
- Blood work: TSH, free T4, thyroglobulin, and TgAb levels are monitored at regular intervals.
For medullary thyroid cancer, monitoring involves calcitonin and CEA levels along with imaging.
Managing Physical Changes
Many thyroid cancer survivors experience ongoing physical challenges even after successful treatment:
- Fatigue: One of the most commonly reported long-term symptoms. Even with optimized thyroid hormone levels, many survivors experience fatigue that is more profound than typical tiredness.
- Weight changes: Both weight gain and difficulty losing weight are common after thyroidectomy. Metabolism shifts and changes in hormone levels contribute to this.
- Temperature sensitivity: Difficulty regulating body temperature, often feeling cold, is a common complaint.
- Brain fog and cognitive changes: Some survivors report difficulty concentrating, memory issues, and "brain fog" that can persist even when blood work appears normal.
Emotional Impact and the "Cancer Lite" Stigma
Many thyroid cancer survivors struggle with a unique emotional burden. Because thyroid cancer has high survival rates, it is sometimes dismissed as the "good cancer" or "easy cancer" by others — even by healthcare professionals. This minimization can lead to:
- Feeling that your experience is not valid or "serious enough" compared to other cancer patients
- Reluctance to seek emotional support or join cancer support groups
- Guilt about struggling when "you should be grateful it is treatable"
- Anxiety about recurrence that feels disproportionate to others' expectations
- Frustration when ongoing symptoms (fatigue, weight changes, brain fog) are dismissed
Your experience is real. Your challenges are valid. Having a treatable cancer does not mean treatment is easy, or that life after treatment returns to normal. If you are struggling emotionally, seek support from a therapist who specializes in cancer patients, or connect with thyroid cancer-specific support communities where people understand what you are going through.
Treatment Side Effects
Understanding potential side effects helps you prepare, recognize them early, and know when to contact your care team.
Hypoparathyroidism (Calcium Issues)
The parathyroid glands are four tiny glands located behind the thyroid that regulate calcium levels in your blood. During thyroid surgery, these glands can be accidentally damaged or removed, leading to low calcium levels (hypocalcemia). Symptoms include:
- Tingling or numbness in the fingertips, toes, and around the lips
- Muscle cramps or spasms
- Severe cases can cause seizures or heart rhythm problems
Temporary hypoparathyroidism occurs in up to 30% of total thyroidectomy patients and usually resolves within weeks to months. Permanent hypoparathyroidism (lasting more than 6 months) occurs in approximately 1 to 3% of cases. Treatment involves calcium supplements and active vitamin D (calcitriol).
Voice Changes
The recurrent laryngeal nerve, which controls the vocal cords, runs directly alongside the thyroid gland. During surgery, this nerve can be stretched, bruised, or (rarely) severed, leading to:
- Hoarseness or a breathy voice quality
- Difficulty projecting your voice or singing
- Voice fatigue after prolonged speaking
- In rare cases of bilateral nerve injury, difficulty breathing may occur
Temporary voice changes occur in up to 10% of patients and usually resolve within weeks to months. Permanent voice changes occur in approximately 1 to 2% of cases. If voice changes persist, referral to a laryngologist and speech-language pathologist can be very helpful.
Radioactive Iodine (RAI) Side Effects
RAI treatment can affect other tissues in the body that naturally absorb iodine, including the salivary glands, tear ducts, and gonads:
- Dry mouth (xerostomia): Salivary gland inflammation and damage is the most common side effect. It can lead to chronic dry mouth, altered taste, and increased risk of dental cavities. Sour candies and adequate hydration during and after treatment can help protect the salivary glands.
- Taste changes: Many patients notice an altered or metallic taste for days to weeks after treatment. This usually resolves but can occasionally persist.
- Nausea: May occur shortly after taking the RAI dose. Anti-nausea medication can help.
- Dry eyes: Tear duct inflammation can cause dry eyes or excessive tearing.
- Fertility considerations: RAI can temporarily affect fertility. Men may experience a temporary decrease in sperm count. Women are advised to wait 6 to 12 months after RAI before becoming pregnant. Discuss fertility preservation options with your care team before treatment if this is a concern.
Hormone Adjustment Period
After thyroidectomy, it takes time to find the right dose of thyroid hormone replacement. During this period, patients may experience symptoms of both hypothyroidism (too little hormone) and hyperthyroidism (too much hormone) as dosages are adjusted:
- Hypothyroid symptoms: Fatigue, weight gain, constipation, dry skin, cold intolerance, depression, brain fog
- Hyperthyroid symptoms: Anxiety, rapid heartbeat, insomnia, tremor, weight loss, heat intolerance
This adjustment period can last several months. Regular blood tests (every 6 to 8 weeks initially) help your doctor fine-tune your medication. Be patient with this process — it takes time, and it is normal to feel "off" during the adjustment period.
Questions to Ask Your Care Team
Copy these questions and bring them to your appointments. Being informed and asking the right questions is one of the most powerful things you can do as a patient.
At Diagnosis
About Surgery
About Radioactive Iodine (RAI)
About Long-Term Follow-Up
Sources & References
Every claim on this page is grounded in the following clinical guidelines, peer-reviewed research, and authoritative cancer resources.
- World Health Organization (WHO). "Thyroid Cancer Fact Sheet." who.int
- American Cancer Society (ACS). "Thyroid Cancer." cancer.org
- National Cancer Institute (NCI). "Thyroid Cancer Treatment (PDQ) — Health Professional Version." cancer.gov
- American Thyroid Association (ATA). "2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer." thyroid.org
- National Comprehensive Cancer Network (NCCN). "NCCN Clinical Practice Guidelines in Oncology: Thyroid Carcinoma." nccn.org
- Haugen BR, Alexander EK, Bible KC, et al. "2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Task Force." Thyroid. 2016;26(1):1–133. doi:10.1089/thy.2015.0020
- Cabanillas ME, McFadden DG, Durante C. "Thyroid cancer." The Lancet. 2016;388(10061):2783–2795. doi:10.1016/S0140-6736(16)30172-6
Last reviewed: January 2025