Thyrotoxicosis vs. hyperthyroidism: What to know

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Hyperthyroidism and thyrotoxicosis are two terms that people incorrectly use interchangeably. However, hyperthyroidism is a subtype of thyrotoxicosis.

Both include high levels of thyroid hormones, but hyperthyroidism refers specifically to excess thyroid hormones from the thyroid gland. Thyrotoxicosis is a broader term that includes the presence of too much thyroid hormone in the body and can occur from other causes.

In this section, we discuss what thyrotoxicosis and hyperthyroidism are.

What is thyrotoxicosis?

Thyrotoxicosis is a clinical state that occurs when individuals have excess thyroid hormone activity in the tissue. It is due to high levels of circulating thyroid hormones in the bloodstream.

Thyrotoxicosis affects approximately 1.2% of people in the United States, and it usually occurs in people ages 20 to 50.

Thyrotoxicosis can range from asymptomatic, which involves no symptoms, to life threatening, causing a dangerous condition known as a thyroid storm. It can affect multiple body systems and may result from various causes, not all of which relate to the overproduction of thyroid hormones by the thyroid gland.

Learn more about thyrotoxicosis and thyroid storm.

What is hyperthyroidism?

Hyperthyroidism is a specific thyroid disorder where the thyroid gland is overactive and produces excessive amounts of thyroid hormones, particularly thyroxine (T4) and triiodothyronine (T3).

This overproduction is commonly due to autoimmune diseases such as Graves’ disease, toxic nodular goiter, or thyroid adenomas.

Hyperthyroidism affects approximately 1 in 100 people over the age of 12 years in the United States and most commonly occurs in individuals over 60 years.

Learn more about hyperthyroidism.

The table below illustrates the similarities and differences.

Both thyrotoxicosis and hyperthyroidism share common symptoms due to high thyroid hormone levels, which can affect the whole body and various body functions. Symptoms can vary from person to person and may include:

• weight loss, despite an increase in appetite
• frequent bowel movements
• diarrhea
• rapid or irregular heartbeat
• anxiety, nervousness, or irritability
• difficulty sleeping or fatigue
• shaky hands
• muscle weakness
• irregular periods
• sweating and heat intolerance
• a goiter, or an enlarged thyroid gland

Older adults may have different symptoms than younger adults with hyperthyroidism, such as loss of appetite or withdrawal from people. Symptoms in older adults are sometimes mistaken for depression or dementia.

Individuals experiencing any symptoms of thyrotoxicosis or hyperthyroidism should seek medical advice. Early diagnosis and treatment are crucial for managing both thyrotoxicosis and hyperthyroidism effectively to prevent further complications.

Severe symptoms warrant immediate medical attention, as they may indicate serious complications like thyroid storm or heart complications. These include:

• chest pain
• difficulty breathing
• confusion

The causes of thyrotoxicosis and hyperthyroidism have some overlap. Thyrotoxicosis occurs due to complications within the thyroid gland or from other tissues in the body. It may also occur due to too much iodine intake and can happen temporarily without hyperthyroidism.

Hyperthyroidism specifically involves the thyroid gland making too much hormone.

Some common causes of both thyrotoxicosis and hyperthyroidism include:

• Graves’ disease
• toxic multinodular goiter
• thyroiditis, inflammation of the thyroid gland
• toxic adenoma, a noncancerous lesion of the thyroid
• struma ovarii
• too much iodine intake
• too much thyroid hormone medication

Identifying the specific cause is crucial for proper treatment.

The treatment for thyrotoxicosis and hyperthyroidism depends on the underlying cause, but it aims to reduce thyroid hormone production and manage symptoms. Treatment may include:

• Medication: Antithyroid drugs like methimazole or propylthiouracil can reduce thyroid hormone production.
• Radioiodine therapy: Also known as radioactive iodine, this treatment destroys overactive thyroid cells.
• Thyroid surgery: This includes partial or total thyroidectomy for pregnant individuals, severe cases, or when other treatments are not successful.

A doctor may also recommend anti-inflammatory drugs to manage inflammation in cases of thyroiditis and beta-blockers to manage symptoms such as rapid heart rate and tremors.

Many of the symptoms of thyrotoxicosis or hyperthyroidism are similar to other health conditions. Therefore, a diagnosis does not include looking at symptoms alone.

A doctor may review an individual’s medical history and then use several tests to confirm the diagnosis and find its cause, including:

• Physical exam: This includes checking for physical symptoms such as a goiter.
• Blood tests: These tests measure levels of thyroid hormones, including T3, T4, and thyroid-stimulating hormone.
• Radioactive iodine uptake test: This is a test to measure how much iodine the thyroid gland absorbs.
• Thyroid scan: This is an imaging test to visualize the structure and function of the thyroid gland.

Hyperthyroidism can cause complications with fertility, so a doctor may recommend tests for individuals who have difficulty getting pregnant.

Without diagnosis and treatment, thyrotoxicosis and hyperthyroidism can lead to severe complications, including:

• Thyroid storm: This is a life threatening condition with extremely high thyroid hormone levels, causing fever, rapid heart rate, and delirium.
• Heart problems: These include an irregular heartbeat, atrial fibrillation, and congestive heart failure.
• Reduction in muscle and bone mass: This can include weakened bones, osteoporosis, and a loss of muscle strength.
• Graves’ ophthalmopathy: This is also known as Graves’ eye disease or thyroid eye disease.
• Thromboembolic disease: This is also known as venous thromboembolism, and it occurs when a blood clot forms in a vein.

In some cases, complications may be fatal. Death rates from a thyroid storm are approximately 8% to 25%. Therefore, it is crucial for a person to seek a diagnosis early.

With appropriate treatment, the outlook for both thyrotoxicosis and hyperthyroidism is generally positive. Early detection and effective management can prevent complications and help individuals lead healthy lives.

Regular follow-ups with healthcare professionals are essential to monitor thyroid function and adjust treatment as necessary.

Preventing thyrotoxicosis involves managing underlying conditions, avoiding excessive thyroid hormone intake, and monitoring thyroid function in individuals at a higher risk of these conditions.

For hyperthyroidism, regular thyroid screenings, especially in individuals with a family history or other risk factors, can help detect and manage the condition early.

Hyperthyroidism is a type of thyrotoxicosis. Both hyperthyroidism and thyrotoxicosis result from excessive thyroid hormones, but they differ in causes and health impacts.

Thyrotoxicosis refers to high thyroid hormone activity in the body, which can arise from various causes. Hyperthyroidism specifically refers to the thyroid gland producing too much hormone.

They require specific approaches to diagnosis and treatment. Understanding their differences is crucial for effective management and prevention of complications.

Through timely medical intervention and appropriate treatment, individuals with these thyroid conditions can have positive outcomes and maintain their quality of life.