OVERVIEW

What is a toxic thyroid adenoma?

Normally, the thyroid-stimulating hormone (TSH) secreted by the pituitary gland acts on thyroid follicular cells, prompting them to synthesize and secrete thyroid hormones. In other words, the thyroid gland follows the commands of the pituitary gland.

However, under certain abnormal conditions, thyroid follicular cells proliferate and form a thyroid adenoma, which does not "obey" the pituitary gland's commands. Instead, it independently and uncontrollably synthesizes and secretes thyroid hormones, leading to hyperthyroidism. This causes increased excitability and hypermetabolism in the nervous, circulatory, digestive, and other systems.

This is called a "toxic thyroid adenoma," also known as an "autonomous functioning thyroid adenoma."

The preferred treatment method is radioactive ¹³¹I therapy.

Is a toxic thyroid adenoma benign or malignant?

Benign. Thyroid adenomas (including toxic thyroid adenomas) are a type of thyroid nodule and are classified as benign nodules.

Who is more likely to develop a toxic thyroid adenoma?

This condition is more common in middle-aged and elderly individuals, and the incidence is relatively higher in inland and mountainous areas with iodine deficiency.

SYMPTOMS

What are the common manifestations of toxic thyroid adenoma?

This condition can cause a series of hyperthyroidism symptoms in patients and may be accompanied by thyroid enlargement. Most patients experience mild symptoms, such as palpitations, weight loss, fatigue, and diarrhea, without exophthalmos. Specific hyperthyroidism symptoms include:

• Skin: Excessive sweating, warm and smooth texture, itching, brittle nails, etc.;

• Cardiovascular system: Palpitations, increased heart rate, elevated blood pressure, etc.;

• Endocrine metabolism: Decreased blood lipids, weight loss, elevated blood sugar;

• Respiratory system: Shortness of breath, especially after activity;

• Digestive system: Increased frequency of bowel movements;

• Genitourinary system: Frequent urination, nocturia, prolonged menstrual cycles, amenorrhea, infertility in women; gynecomastia, decreased libido, erectile dysfunction, infertility in men, etc.;

• Bones: Osteoporosis, increased risk of fractures;

• Neurological and psychiatric systems: Hand tremors, anxiety, irritability, mood swings; elderly patients may exhibit emotional apathy.

Can toxic thyroid adenoma lead to serious consequences?

If left uncontrolled for an extended period, this condition can damage the heart, potentially leading to heart failure or even sudden death. Severe cases may develop thyroid storm, which is life-threatening.

CAUSES

What are the causes of toxic thyroid adenoma?

The specific cause of toxic thyroid adenoma is still unclear, but it may be related to gene mutations in the thyroid-stimulating hormone receptor and G protein, as well as iodine deficiency.

Is toxic thyroid adenoma hereditary?

This disease has some hereditary tendency, but it does not necessarily mean it will definitely appear in offspring.

DIAGNOSIS

What tests are needed for toxic thyroid adenoma?

Most patients with toxic thyroid adenoma have no obvious symptoms and may only discover thyroid nodules incidentally during physical examinations. After detecting thyroid nodules, the following tests are usually required:

• Thyroid ultrasound: Used to evaluate thyroid size, shape, texture, nodule size, and quantity, providing a preliminary assessment of nodule characteristics.
• Thyroid function tests: Used to diagnose whether the thyroid nodule causes hyperthyroidism and determine its severity.
• Thyrotropin receptor antibody (TRAb): Used to differentiate whether hyperthyroidism is caused by Graves' disease, as a positive result typically indicates Graves' disease.
• Thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb): Used to assist in diagnosing concurrent thyroid diseases, such as Hashimoto's thyroiditis.
• Thyroid scintigraphy: Used to confirm the diagnosis of toxic thyroid adenoma. In scintigraphy, the adenoma appears as a "hot nodule," while surrounding tissues may atrophy and show reduced or no uptake.

Which diseases are easily confused with toxic thyroid adenoma?

This condition is often confused with hyperthyroidism caused by toxic multinodular goiter, pituitary thyrotropin-secreting adenoma, or Graves' disease. It may also be mistaken for transient thyrotoxicosis due to autoimmune thyroiditis (e.g., Hashimoto's thyroiditis). The above-mentioned common manifestations and relevant tests can help doctors differentiate these conditions.

TREATMENT

Which department should I visit for toxic thyroid adenoma?

Endocrinology, General Internal Medicine, or Thyroid Surgery (or Thyroid and Breast Surgery).

Does toxic thyroid adenoma always require treatment?

If the patient exhibits obvious hyperthyroidism—i.e., thyroid function tests show thyroid-stimulating hormone (TSH) below the normal range, and free thyroxine (FT4) and/or triiodothyronine (T3) above the normal range—treatment is necessary.

If thyroid function tests indicate only TSH below the normal range, with FT4 and T3 within normal limits (subclinical hyperthyroidism), the need for treatment depends on the doctor's assessment of hyperthyroidism complication risks and TSH levels. For details, see Subclinical Hyperthyroidism.

How is toxic thyroid adenoma treated?

Treatment options include: radioactive ¹³¹I therapy, surgical treatment, and thiourea drug therapy.

• Radioactive ¹³¹I therapy or surgical thyroidectomy is the preferred treatment, as it can cure the condition. If thyroid enlargement compresses the trachea or esophagus, or if thyroid cancer is present, surgery is prioritized.

• Long-term thiourea drug therapy (e.g., methimazole or propylthiouracil) is another option, though it does not cure the disease.

• For patients unwilling or unable to undergo the above treatments, ethanol injection under ultrasound guidance, or radiofrequency ablation/laser therapy to destroy the adenoma may be considered. However, the efficacy and safety of these methods require further evaluation.

• Beta-blockers (e.g., propranolol or atenolol) can be used alongside radioactive ¹³¹I therapy, surgery, or thiourea drugs to control symptoms like palpitations and tremors.

What precautions should be taken for radioactive ¹³¹I therapy?

Before treatment: Discontinue methimazole for 3 days or propylthiouracil for at least 2 weeks, avoid iodine-containing vitamins for 7–10 days, avoid iodine-rich foods and medications for 2–3 weeks, and stop amiodarone for 3–6 months.

After treatment: Since ¹³¹I is radioactive:

• Drink plenty of water and urinate frequently within the first 2 days.

• Stay at home for the first week, maintain a distance of at least 1.8 meters from others, and avoid sharing utensils.

• Minimize close contact with family members, especially children and pregnant women, for the first month.

• Use a separate bathroom if possible, and flush multiple times after use to prevent contamination.

• Avoid pregnancy for 6 months post-treatment.

What should pregnant women do if toxic thyroid adenoma is suspected?

Pregnant women cannot undergo thyroid scintigraphy, making diagnosis impossible. Radioactive ¹³¹I therapy is also contraindicated.

If hyperthyroidism with thyroid nodules is detected during pregnancy, thiourea drugs should be used to stabilize thyroid function.

Propylthiouracil is recommended in the first trimester; methimazole may be used afterward. Short-term, low-dose beta-blockers can also help manage symptoms.

After breastfeeding ends, thyroid scintigraphy can confirm the diagnosis and adjust treatment.

Is follow-up necessary after toxic thyroid adenoma treatment? How?

Yes.

• After radioactive ¹³¹I therapy: Monitor thyroid function every 4–6 weeks for six months. If remission is confirmed, extend intervals to at least annually.

• After surgery: Monitor thyroid function every 6–8 weeks if thyroid hormone replacement is needed.

• For patients on antithyroid drugs: Monitor thyroid function every 4–6 weeks, along with liver function and blood tests, until stable.

Can toxic thyroid adenoma be cured?

Yes, with radioactive ¹³¹I therapy or surgery.

DIET & LIFESTYLE

What should patients with toxic thyroid adenoma pay attention to in daily life?

Since toxic thyroid adenoma can cause hyperthyroidism, the precautions are the same as for hyperthyroidism patients.

• Maintain a comprehensive and balanced diet with adequate intake of protein-rich and vitamin-rich foods.

• Avoid iodine-rich foods unless pregnant or breastfeeding.

• Avoid alcohol, tea, and coffee.

• Quit smoking.

• Ensure sufficient sleep and maintain an optimistic, relaxed mood.

Can patients with toxic thyroid adenoma have normal fertility?

It is best for patients with this condition to conceive only after their condition has stabilized, thyroid function has normalized, or they have been completely cured. Female patients taking antithyroid drugs who urgently wish to become pregnant should switch to propylthiouracil.

PREVENTION

Can Toxic Thyroid Adenoma Be Prevented?

This disease is common in iodine-deficient areas and may be related to iodine deficiency. Residents in non-high-water-iodine areas should consume iodized salt.