OVERVIEW

What is hyperthyroidism?

Hyperthyroidism, hereinafter referred to as hyperthyroidism, is caused by excessive secretion of thyroid hormones. Symptoms may include heat intolerance, excessive sweating, palpitations, insomnia, increased appetite, and weight loss^[1].

The causes of hyperthyroidism vary and include Graves' disease, toxic multinodular goiter, and thyroid autonomous hyperfunctioning adenoma. Among these, hyperthyroidism caused by Graves' disease is the most common^[1].

This condition can generally be treated with oral medications, radioactive iodine-131 therapy, or surgery. Most patients can be cured, while a small number may experience relapse or require lifelong treatment.

Is hyperthyroidism the same as "big neck disease"?

No.

"Big neck disease" is caused by widespread iodine deficiency in the diet and is medically known as "endemic goiter." Due to the widespread use of iodized salt, this condition is now rare. Both hyperthyroidism and "big neck disease" can cause thyroid enlargement, but hyperthyroidism is also accompanied by symptoms in other systems, such as palpitations and diarrhea, whereas "big neck disease" typically does not present with other systemic symptoms. The two can be distinguished through thyroid function tests.

Is hyperthyroidism common?

Yes. In China, the prevalence of hyperthyroidism is approximately 1.5%^[2], meaning about 3 in every 200 people have this condition.

SYMPTOMS

What are the symptoms of hyperthyroidism?

The most common symptoms of hyperthyroidism include fatigue, heat intolerance, excessive sweating, warm and moist skin, low-grade fever, weight loss, and thyroid enlargement. Additionally, the following symptoms may occur:

• Nervous system: Irritability, excitability, insomnia, nervousness, anxiety, restlessness, and difficulty concentrating.
• Eye manifestations: Bulging eyes (exophthalmos), eye swelling and pain, photophobia, tearing, double vision, and decreased vision.
• Cardiovascular system: Palpitations and shortness of breath, which worsen with physical activity.
• Digestive system: Increased appetite, accompanied by frequent bowel movements or diarrhea. A few patients may experience nausea and vomiting.
• Endocrine system: Women often experience reduced menstrual flow, prolonged menstrual cycles, or even amenorrhea. Men may develop erectile dysfunction, and occasionally gynecomastia^[3].

What causes bulging eyes in hyperthyroidism?

• Mild bulging eyes (exophthalmos) may be related to increased thyroid hormone levels stimulating the sympathetic nervous system, which can be understood as "hyperthyroid patients appearing more alert, so their eyes open wider." This condition is called "simple exophthalmos."

• Moderate to severe exophthalmos is seen in Graves' disease (diffuse toxic goiter). In this case, "exophthalmos" and hyperthyroidism do not necessarily occur simultaneously, nor do they always resolve together^[3].

Will exophthalmos improve once hyperthyroidism is treated?

The aforementioned "simple exophthalmos," which generally involves no tissue proliferation, usually improves as hyperthyroidism is controlled.

However, exophthalmos caused by Graves' disease often does not fully resolve and may require additional treatments, such as glucocorticoid therapy, radiation therapy, or even surgery^[3].

Can exophthalmos caused by hyperthyroidism be cured?

The effectiveness of treatment for hyperthyroid exophthalmos depends on the severity of the condition.

Hyperthyroid exophthalmos is divided into simple exophthalmos and infiltrative exophthalmos. Simple exophthalmos and mild infiltrative exophthalmos usually improve as hyperthyroidism is treated, with a good prognosis. Moderate to severe active infiltrative exophthalmos is often difficult to cure completely.

Comprehensive treatment includes:

• Active treatment of hyperthyroidism.
• Eye care: Avoid exposure to bright light, use artificial tears, and prevent prolonged corneal exposure to air.
• Systemic therapy: Glucocorticoids, other immunosuppressants, monoclonal antibody drugs, orbital radiation therapy, or orbital decompression surgery.

What is a thyroid storm?

Thyroid storm, also known as hyperthyroid crisis, mostly occurs in patients with severe hyperthyroidism who have not received standardized treatment. It is characterized by high fever, rapid heartbeat (heart rate >140 beats per minute), profuse sweating, nausea, vomiting, and, in severe cases, heart failure, shock, and coma.

Thyroid storm is life-threatening, with a mortality rate exceeding 20%^[1]. This means that out of 100 patients experiencing a thyroid storm, about 20 may die.

CAUSES

What are the causes of hyperthyroidism?

• Diffuse toxic goiter: This is the most common cause of hyperthyroidism^[1].
• Toxic nodular goiter and autonomous hyperfunctioning thyroid adenoma: These can also lead to excessive thyroid hormone production, causing hyperthyroidism^[1].
• Other causes include excessive iodine intake or use of iodine-containing medications (such as amiodarone), pituitary disorders, smoking, high-iodine diets, infections, pregnancy, etc.^[3].

What is diffuse toxic goiter, the primary cause of hyperthyroidism?

Diffuse toxic goiter is an autoimmune disease that can lead to hyperthyroidism and may be associated with genetic factors or immune system abnormalities. Its characteristic features include exophthalmos (bulging eyes) and diffuse thyroid enlargement^[1].

What is Graves' disease, a major cause of hyperthyroidism?

Graves' disease is an autoimmune disorder that can cause hyperthyroidism. It is characterized by exophthalmos and significantly elevated levels of the autoantibody TRAb in the blood.

Who is more likely to develop hyperthyroidism?

• Individuals with a family history of diffuse toxic goiter: The disease has a strong genetic predisposition, so those with a family history are at higher risk of developing hyperthyroidism^[1].
• Pregnant women: Pregnant women are also a high-risk group for hyperthyroidism, possibly due to the placenta releasing large amounts of human chorionic gonadotropin (hCG).
• People who consume high-iodine diets or use iodine-containing medications long-term: They are more prone to hyperthyroidism than the general population, likely because excessive iodine disrupts normal thyroid function.

Is hyperthyroidism hereditary?

Hyperthyroidism caused by autoimmune thyroid diseases (such as diffuse toxic goiter) may be hereditary, but it is not guaranteed to be passed down^[1].

Is hyperthyroidism contagious?

No.

DIAGNOSIS

How do doctors diagnose hyperthyroidism?

• Generally, doctors diagnose the condition based on the patient's medical history (previous thyroid or autoimmune diseases), medication use (such as amiodarone or thyroid hormones), personal history (high-iodine diet, pregnancy), family history (autoimmune thyroid diseases in relatives), and clinical manifestations, combined with thyroid function tests^[3].

• However, some patients may have atypical symptoms, so doctors may also order thyroid ultrasound, thyroid radionuclide imaging, orbital CT, or other tests.

What tests are needed to diagnose hyperthyroidism?

• Thyroid function tests: Common indicators include total triiodothyronine (TT3), free triiodothyronine (FT3), total thyroxine (TT4), free thyroxine (FT4), and thyroid-stimulating hormone (TSH). These indicators directly reflect thyroid function status^[3].
• Thyroid autoantibody tests: Common indicators include thyroid-stimulating hormone receptor antibody (TRAb), thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb). These help determine the cause and disease activity of hyperthyroidism^[3].
• Thyroid ultrasound: A convenient, fast, and non-invasive method to observe thyroid morphology and size changes, aiding clinical diagnosis and treatment.
• Thyroid radionuclide imaging: The patient ingests or is injected with a tracer, which the thyroid absorbs before being scanned to clearly display its position, size, shape, and any enlargement or ectopia.
• Orbital CT or MRI: For patients with exophthalmos, these tests evaluate eye position and extraocular muscle size^[3].
• Radioactive iodine uptake (RAIU): Helps differentiate the cause of hyperthyroidism, as iodine uptake varies significantly depending on the underlying condition^[3].

If TSH is low or high but T₃, T₄ are normal, is it hyperthyroidism?

Not necessarily.

Low TSH with normal T₃, T₄ suggests "subclinical hyperthyroidism";
High TSH with normal T₃, T₄ suggests "subclinical hypothyroidism."

Over time, subclinical hyperthyroidism or hypothyroidism may progress to overt hyperthyroidism or hypothyroidism.

What is radioactive iodine uptake (RAIU) in hyperthyroidism testing?

RAIU helps distinguish the cause of hyperthyroidism, as iodine uptake patterns differ significantly depending on the underlying condition. It is also used for selecting patients for radioactive iodine-131 therapy and guiding treatment planning.

TREATMENT

Which department should I see for hyperthyroidism?

Endocrinology.

Does subclinical hyperthyroidism in hyperthyroidism require treatment?

Most people do not need treatment and can have their thyroid function checked regularly to monitor disease progression.

A small number of subclinical hyperthyroidism patients may require treatment if the following conditions occur:

• Symptoms of hyperthyroidism, such as heat intolerance, excessive sweating, palpitations, hand tremors, increased appetite, or significant weight loss.

• Age 65 or older and not treated with radioactive ¹³¹I therapy.

• Age under 65 with TSH levels < 0.1 mU/L.

Can hyperthyroidism be cured? How is it treated?

In some cases, yes.

There are three main treatment methods for hyperthyroidism: oral medication, radioactive iodine-131 therapy, or surgery. Some patients can achieve a cure, while others may experience recurrence or require lifelong treatment.

Medication for hyperthyroidism includes antithyroid therapy and symptomatic treatment.

• Antithyroid therapy: Methimazole is the first choice. If allergic or during pregnancy planning/pregnancy, propylthiouracil may be considered.
• Symptomatic treatment: Includes lowering heart rate (to alleviate palpitations and tremors), correcting electrolyte imbalances (e.g., potassium supplementation), protecting liver function, and increasing white blood cell counts.

Radioactive iodine-131 therapy may be considered for patients with: Significant thyroid enlargement or recurrent hyperthyroidism despite medication.

Surgery is recommended for patients with: Significant thyroid enlargement causing compression symptoms, substernal goiter, or concurrent thyroid cancer.

What oral antithyroid drugs are used for hyperthyroidism? Which one should I take?

The two commonly used oral antithyroid drugs are methimazole and propylthiouracil.

• Methimazole is the first choice for most people because it is taken once daily, slightly more effective than propylthiouracil, and has fewer liver-related side effects.
• Pregnant women in the first trimester should preferably take propylthiouracil, as it crosses the placenta less and has fewer effects on the fetus. However, propylthiouracil carries a higher risk of liver damage, so switching back to methimazole may be considered in later pregnancy^[1,3].

For more specific cases, consult your doctor.

What are the side effects of oral antithyroid drugs for hyperthyroidism?

The side effects of the two common oral antithyroid drugs are similar, including liver damage, decreased white blood cell counts, rashes, and vasculitis^[1,3].

Due to these side effects, blood tests and liver function monitoring are required before and during treatment. Consult your doctor for specific monitoring schedules^[1,3].

Can I continue taking antithyroid drugs if my liver function or blood tests are abnormal?

Mild abnormalities may allow continued use with liver-protective or white blood cell-boosting therapy, along with close monitoring.

Severe liver dysfunction or significant blood abnormalities require immediate discontinuation and symptomatic treatment.

Consult your doctor for specific guidance.

How often should thyroid function be checked after starting antithyroid medication?

• After starting medication, thyroid function should be checked every 4 weeks to adjust dosage^[1].

• During the stable phase, monitoring is typically every 2 months^[1]. Consult your doctor for specifics.

Why does my doctor prescribe thyroid hormone alongside antithyroid medication?

If T₃ and T₄ levels drop near the lower limit while TSH rises above normal during dosage reduction, small doses of thyroid hormone may be added to suppress TSH back to normal range—an empirical treatment approach.

Why does hyperthyroidism recur after recovery?

Hyperthyroidism is prone to recurrence, even after thyroid function normalizes or medication is stopped. Excessive iodine intake may contribute^[1].

When is radioactive ¹³¹I therapy needed?

Radioactive ¹³¹I therapy or surgery may be considered if:

• Severe allergic reactions or side effects prevent continued medication.
• Full-dose medication fails to control thyroid function.
• Hyperthyroidism recurs frequently.

Consult your doctor for specifics^[1].

Is radioactive ¹³¹I therapy for hyperthyroidism the same as radiation therapy? What are its effects?

Radioactive ¹³¹I is localized radiation therapy. Since iodine concentrates in the thyroid, its impact on surrounding tissues is minimal compared to conventional radiation^[1].

Is hypothyroidism after radioactive ¹³¹I therapy permanent?

Hypothyroidism is the most common complication and is often permanent.

However, hypothyroidism is easier to manage than hyperthyroidism—oral thyroid hormone replacement can effectively restore normal function with proper dosing.

Other rare complications include radiation thyroiditis, thyroid storm in severe untreated cases, and worsening eye disease in Graves' ophthalmopathy^[1].

How is hyperthyroidism treated during pregnancy?

Medication is the primary treatment, with propylthiouracil preferred in early pregnancy. Thyroid function should be monitored more frequently^[1].

Radioactive ¹³¹I is contraindicated. Surgery may be an option in the second trimester.

When is surgery needed for hyperthyroidism?

Surgery is recommended for:

• Significant thyroid enlargement causing compression symptoms.
• Concurrent thyroid cancer or substernal goiter.

Options include subtotal or total thyroidectomy^[3].

• Subtotal thyroidectomy preserves some thyroid tissue but has an ~8% recurrence rate^[3].

• Total thyroidectomy has near-zero recurrence but requires lifelong thyroid hormone replacement^[3].

What is the first-line treatment for hyperthyroidism?

Treatment options include antithyroid drugs (ATD), radioactive iodine (¹³¹I), and surgery. The choice depends on disease severity, thyroid size, and patient preference.

1. Antithyroid drugs (methimazole/propylthiouracil) are first-line but require 1–2 years of treatment with a ~50% remission rate. Recurrence is common during dose reduction.
2. Radioactive iodine is effective for refractory cases, with a 52.6–77% cure rate. Hypothyroidism is a common long-term outcome.
3. Surgery is indicated for large goiters, compression symptoms, or suspected malignancy. Complications include nerve damage or hypoparathyroidism.

In China, ATD is typically tried first, while radioactive iodine is often preferred in Western countries. Surgery is prioritized for severe cases or suspected cancer.

Can I stop medication if my thyroid function tests normalize?

Hyperthyroidism treatment involves three phases: full dose, tapering, and maintenance. Even after normalization, maintenance therapy (e.g., half or one tablet daily) is needed.

Most patients achieve normal thyroid hormone levels within ~13 months, but TSH receptor antibodies may take ~1.5 years to normalize.

Treatment typically lasts 1.5–2 years. Stopping requires two negative TSH receptor antibody tests 3 months apart to reduce relapse risk.

Post-treatment monitoring is essential due to high recurrence rates.

DIET & LIFESTYLE

Can people with hyperthyroidism not eat iodine-rich foods?

• After being diagnosed with hyperthyroidism, iodine-rich foods such as kelp and nori should be avoided, and it is recommended to use non-iodized salt for cooking. Iodine intake is closely related to the stability and recurrence of hyperthyroidism^[1,4].
• Due to increased metabolism, hyperthyroidism patients often experience significant weight loss. Therefore, sufficient calories, nutrients, and proteins should be supplemented, such as steamed buns, bread, beef, and fish^[4].
• Additionally, healthy lifestyle habits like quitting smoking, limiting alcohol, exercising regularly, maintaining a regular schedule, and eating a balanced diet are beneficial for any disease.

What dietary precautions should be taken for hyperthyroidism?

The dietary principle for hyperthyroidism is to provide foods high in calories, protein, carbohydrates, and vitamins, while increasing calcium and phosphorus intake.

Eat regularly in small, frequent meals, avoiding overeating at one time. You can add 2–3 extra snacks per day, such as small portions of staple foods, fruits, or nuts.

Engage in moderate exercise to strengthen immunity, balance work and rest, and avoid excessive fatigue.

Stay adequately hydrated, drinking 1500–3000 mL of water daily (about 3–6 bottles of 500 mL mineral water) to promote metabolism. Avoid coffee, strong tea, alcohol, and stimulating energy drinks.

Use non-iodized salt and avoid high-iodine seafood like kelp and nori, as well as spicy and irritating foods and seasonings.

Processed foods, salted nuts, cheese, and spicy snacks are high in salt. If consumed, portion control is essential. Opt for unsalted nuts and cheese.

Does hyperthyroidism affect pregnancy?

Hyperthyroidism can lead to miscarriage, premature birth, stillbirth, or even thyroid storm in pregnant women. If the condition is uncontrolled, pregnancy is not recommended.

For patients undergoing medication, pregnancy is advisable only after serum total triiodothyronine (T3) and thyroxine (T4) levels normalize and medication is discontinued for at least 3 months^[1].

Can breastfeeding mothers with hyperthyroidism take antithyroid drugs?

Theoretically, current research suggests oral antithyroid drugs are safe for infants, and breastfeeding mothers can take them, with methimazole being the preferred choice.

The ideal timing is to take the medication right after breastfeeding or 3–4 hours before the next feeding^[5]. Breast milk within four hours after taking the drug should be discarded.

Can people with hyperthyroidism exercise?

Moderate exercise is beneficial for everyone, including hyperthyroidism patients. If the condition is well-controlled without cardiac complications, mild activities like jogging or yoga are acceptable. After recovery, normal exercise can be resumed.

What should hyperthyroidism patients pay attention to in daily life?

• Take medications as prescribed, attend regular follow-ups, and avoid arbitrarily reducing, changing, or stopping treatment.
• Get adequate rest and avoid overexertion.
• Avoid emotional stress and excessive pressure. Choose relaxing activities like listening to music or watching movies, but avoid eye strain.

PREVENTION

Can hyperthyroidism be prevented?

Yes, it can be prevented.

• Receive health education about the disease to improve awareness of hyperthyroidism.
• Pay attention to avoiding long-term, excessive consumption of high-iodine seafood such as kelp and seaweed to prevent excessive iodine intake.