Hyperthyroidism

Jai Ganesh · 2025-02-19 17:10:34

Hyperthyroidism

Gist

Hyperthyroidism happens when the thyroid gland makes too much thyroid hormone. This condition also is called overactive thyroid. Hyperthyroidism speeds up the body's metabolism. That can cause many symptoms, such as weight loss, hand tremors, and rapid or irregular heartbeat.

Summary

Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidism. Some, however, use the terms interchangeably. Signs and symptoms vary between people and may include irritability, muscle weakness, sleeping problems, a fast heartbeat, heat intolerance, diarrhea, enlargement of the thyroid, hand tremor, and weight loss. Symptoms are typically less severe in the elderly and during pregnancy. An uncommon but life-threatening complication is thyroid storm in which an event such as an infection results in worsening symptoms such as confusion and a high temperature; this often results in death. The opposite is hypothyroidism, when the thyroid gland does not make enough thyroid hormone.

Graves' disease is the cause of about 50% to 80% of the cases of hyperthyroidism in the United States. Other causes include multinodular goiter, toxic adenoma, inflammation of the thyroid, eating too much iodine, and too much synthetic thyroid hormone. A less common cause is a pituitary adenoma. The diagnosis may be suspected based on signs and symptoms and then confirmed with blood tests. Typically blood tests show a low thyroid stimulating hormone (TSH) and raised T3 or T4. Radioiodine uptake by the thyroid, thyroid scan, and measurement of antithyroid autoantibodies (thyroidal thyrotropin receptor antibodies are positive in Graves disease) may help determine the cause.

Treatment depends partly on the cause and severity of disease. There are three main treatment options: radioiodine therapy, medications, and thyroid surgery. Radioiodine therapy involves taking iodine-131 by mouth which is then concentrated in and destroys the thyroid over weeks to months. The resulting hypothyroidism is treated with synthetic thyroid hormone. Medications such as beta blockers may control the symptoms, and anti-thyroid medications such as methimazole may temporarily help people while other treatments are having an effect. Surgery to remove the thyroid is another option. This may be used in those with very large thyroids or when cancer is a concern. In the United States hyperthyroidism affects about 1.2% of the population. Worldwide, hyperthyroidism affects 2.5% of adults. It occurs between two and ten times more often in women. Onset is commonly between 20 and 50 years of age. Overall the disease is more common in those over the age of 60 years.

Details

Hyperthyroidism, also called overactive thyroid, happens when your thyroid makes and releases high levels of thyroid hormone. It speeds up several bodily functions, causing symptoms like rapid heart rate, weight loss, increased appetite and anxiety. Hyperthyroidism is treatable — typically with medications.

Overview:

What is hyperthyroidism?

Hyperthyroidism, also called overactive thyroid, is a condition where your thyroid makes and releases high levels of thyroid hormone. It has multiple possible causes. The main thyroid hormones are triiodothyronine (T3), thyroxine (T4) and thyroid stimulating hormone (TSH).

Hyperthyroidism speeds up your metabolism, which can affect several aspects of your health. The condition can throw your whole well-being off balance. You may not feel like yourself or even feel out of control of your body. It’s important to get medical treatment if you develop signs of hyperthyroidism so you can get back to feeling like yourself.

How common is hyperthyroidism?

Hyperthyroidism is relatively rare. Approximately 1.3% of people in the United States have it.

Symptoms and Causes:

What are the symptoms of hyperthyroidism?

Hyperthyroidism can impact your entire body, so there are many symptoms. You may experience some of these symptoms and not others, or many of them at the same time. Symptoms of hyperthyroidism can include:

* Rapid heart rate (tachycardia) and/or heart palpitations.
* Increased blood pressure.
* Shakiness, like hand tremors.
* Feeling anxious, nervous and/or irritable.
* Weight loss despite a regular or increased appetite.
* Diarrhea or more frequent pooping.
* Increased sweating and sensitivity to warm temperatures.
* Hair loss or brittle hair.
* Difficulty sleeping (insomnia).
* Menstrual period changes, like lighter or missed periods.
* Swelling and enlargement of your neck (goiter).
* Swelling or bulging of your eyes (thyroid eye disease).

These symptoms can start suddenly or develop slowly over time. It’s important to see your healthcare provider if you develop hyperthyroidism symptoms.

What causes hyperthyroidism?

Medical conditions and situations that can cause hyperthyroidism include:

* Graves’ disease: This is an autoimmune condition that makes your thyroid overactive. Graves’ disease is the most common cause of hyperthyroidism. Your chances of developing it increase if you have a biological family history of thyroid disease and/or another autoimmune condition.
* Thyroid nodules: These are lumps or growths of cells in your thyroid gland. They can sometimes produce excess thyroid hormone. Healthcare providers may call this toxic multinodular goiter (TMNG). Thyroid nodules are rarely cancerous.
* Thyroiditis: Thyroiditis is inflammation of your thyroid gland. It can cause hyperthyroidism temporarily. After this phase — the thyrotoxic phase — it may cause hypothyroidism (underactive thyroid). When the inflammation goes away, your hormone levels may stabilize.
* Consuming excess iodine: Consuming too much iodine (through foods or medications) can cause your thyroid to produce more thyroid hormone. Iodine is a mineral that your thyroid uses to create thyroid hormone. Receiving IV iodinated contrast (iodine “dye”) or taking amiodarone (a medication) may cause hyperthyroidism.
* TSH-releasing pituitary adenoma (thyrotropinoma): This is a growth in your pituitary gland that releases excess thyroid-stimulating hormone (TSH). Your pituitary gland normally releases TSH to trigger your thyroid to release thyroid hormone. Excess TSH can lead to excess thyroid hormone. This is a very rare cause of hyperthyroidism.

What are the risk factors for hyperthyroidism?

Factors that increase your risk of developing hyperthyroidism include:

* Biological family history of thyroid disease and/or autoimmune conditions.
* Smoking.
* Pregnancy (for postpartum thyroiditis).

Diagnosis and Tests:

How is hyperthyroidism diagnosed?

The diagnostic process for hyperthyroidism may involve multiple steps, including:

* A physical exam: To start, your healthcare provider will do a physical exam to check for signs of hyperthyroidism, like an enlarged thyroid, rapid heart rate and warm, moist skin.
* Thyroid blood tests: Blood tests can check your thyroid hormone levels. When you have hyperthyroidism, levels of the thyroid hormones T3 and T4 are above normal and thyroid-stimulating hormone (TSH) is often (but not always) lower than normal.
* Thyroid antibody blood test: This test can check if Graves’ disease is the cause.
* Imaging tests: Various imaging tests of your thyroid can help diagnose hyperthyroidism and its cause. They include a radioactive iodine uptake (RAIU) test and scan and a thyroid ultrasound.

Your provider will go over the options and processes with you and recommend the test they think is best.

Additional Information

Hyperthyroidism is excess production of thyroid hormone by the thyroid gland. Most patients with hyperthyroidism have an enlarged thyroid gland (goitre), but the characteristics of the enlargement vary. Examples of thyroid disorders that give rise to hyperthyroidism include diffuse goitre (Graves disease), toxic multinodular goitre (Plummer disease), and thyroid inflammation (thyroiditis). Hyperthyroidism occurs more often in adults than in children, and it is 5 to 10 times more common in women than in men.

Causes of hyperthyroidism

The most common cause of hyperthyroidism is Graves disease, named for the Irish physician Robert Graves, who was among the first to describe the condition. Graves disease is an autoimmune disorder in which hyperthyroidism and goitre are caused by thyroid-stimulating antibodies. These antibodies bind to and activate thyrotropin (thyroid-stimulating hormone; TSH) receptors on the thyroid gland, thereby mimicking the actions of thyrotropin. Risk factors for Graves disease include gender (women are affected more often than men), smoking, and a high intake of iodine. In addition, some individuals possess genetic susceptibility to the disease. The immediate events that lead to the production of thyroid-stimulating antibodies that cause hyperthyroidism are not known, although emotional stress has been postulated to be an important factor. An interesting feature of Graves disease is spontaneous remission, with a disappearance of the thyroid-stimulating antibodies. In these patients, antithyroid drug treatment can be withdrawn without recurrence of hyperthyroidism.

Approximately 25 to 35 percent of patients with Graves disease have Graves ophthalmopathy. The defining characteristic of this condition is the protrusion of the eyes (exophthalmos). The eyelids may be retracted upward, making it seem as though the person is constantly staring. The tissues surrounding the eyes may swell, and the eye muscles may not function properly, causing double vision. In rare cases, vision is decreased because of compression or stretching of the optic nerve. These changes are caused by swelling and inflammation of the eye muscles and the adipose (fat) tissue behind the eyes. Approximately 1 to 2 percent of patients with Graves disease have localized myxedema, which is characterized by circumscribed thickening of the skin and subcutaneous tissue on the lower legs (pretibial myxedema), arms, or trunk. Nearly all patients with localized myxedema have severe ophthalmopathy and have had hyperthyroidism in the past. Ophthalmopathy and localized myxedema are believed to be caused by both antibody-mediated and cell-mediated immunologic mechanisms. Whether the antibodies are thyroid-stimulating antibodies or different antibodies is not known.

The second most common cause of hyperthyroidism is toxic multinodular goitre, or Plummer disease. This condition begins early in life and is due to iodine deficiency or to other factors that decrease thyroid hormone secretion and result in a persistent increase in thyrotropin secretion and therefore persistent thyroid gland stimulation. This stimulation initially causes generalized thyroid enlargement, but, as time passes, localized regions of the gland grow and function independently of thyrotropin. A less common cause of hyperthyroidism is a benign tumour (toxic adenoma) of the thyroid gland. In many cases these tumours contain a mutation of the thyrotropin receptor gene that results in the synthesis of thyrotropin receptors that are active and therefore lead to excess thyroid hormone production in the absence of thyrotropin.

Several types of thyroiditis can result in the release of stored thyroid hormone in amounts sufficient to cause hyperthyroidism. One type, called silent lymphocytic thyroiditis, is painless and is particularly common in women in the first year after a pregnancy (postpartum thyroiditis). Another type, called subacute granulomatous thyroiditis, is characterized by thyroid pain and tenderness. Hyperthyroidism in patients with thyroiditis is usually mild and self-limiting, lasting only until the stores of hormone in the thyroid gland are exhausted.

The administration of high doses of thyroid hormone is a common cause of hyperthyroidism. The hormone may have been given by a physician to treat hypothyroidism or to decrease the size of a goitre. In addition, some patients purchase thyroid hormone from health and nutrition stores in the form of a crude thyroid extract or an analogue of thyroid hormone purported to stimulate metabolism and cause weight loss. These preparations may contain variable amounts of thyroid hormone and can have unpredictable effects on the body.

In rare cases, hyperthyroidism may be caused by a thyrotropin-secreting tumour of the pituitary gland or a struma ovarii, in which hyperfunctioning thyroid tissue is present in a tumour of the ovary.

Symptoms of hyperthyroidism

The onset of hyperthyroidism is usually gradual but can be sudden. The increase in thyroid hormone secretion results in an increase in the function of many organ systems. The cardiovascular and neuromuscular systems are likely to be affected. The cardiovascular symptoms and signs of hyperthyroidism include an increase in heart rate (tachycardia), atrial fibrillation (rapid irregular heart rhythm), palpitations (pounding in the chest due to forceful contraction of the heart), shortness of breath, and exercise intolerance. Neuromuscular symptoms and signs of hyperthyroidism include nervousness, hyperactivity and restlessness, anxiety and irritability, insomnia, tremor, and muscle weakness. Other common symptoms and signs of hyperthyroidism are weight loss despite a good or even increased appetite, increased perspiration and intolerance of heat, increased frequency of bowel movements, and irregular menstrual cycles and decreased menstrual blood flow in women. Hyperthyroidism also causes an increase in bone resorption and therefore contributes to osteoporosis. The most severe form of hyperthyroidism is thyroid storm. This acute condition is characterized by very rapid heart rate, fever, hypertension (high blood pressure), and certain gastrointestinal and neurological symptoms and may result in heart failure, hypotension (low blood pressure), shock, and death.

Diagnosis of hyperthyroidism

Hyperthyroidism is diagnosed based on the symptoms and signs described above and on measurements of high serum total and free thyroid hormone concentrations and low, sometimes undetectable, serum thyrotropin concentrations. In serum, there are actually two thyroid hormones, thyroxine and triiodothyronine, with the former being produced in much greater quantities than the latter. Thyroid hormones exist in two forms, one of which is bound to several proteins, and the other of which, a very small amount, is free. Thus, serum thyroxine can be measured as serum total thyroxine or free thyroxine; the latter is preferable because it is the form of thyroxine that is readily available to the cells of the body and, therefore, is metabolically active. Measurements of serum total thyroxine are high in patients with thyroid disease and in patients producing more of the proteins that bind to thyroxine.

The cause of hyperthyroidism may be distinguished based on relative differences in the concentrations of thyroxine, triiodothyronine, and thyrotropin. Patients with a thyrotropin-secreting pituitary tumour have normal or high serum thyrotropin concentrations. Rarely, patients have normal serum thyroxine concentrations but high serum triiodothyronine concentrations. These patients are said to have triiodothyronine thyrotoxicosis. Other patients have low serum thyrotropin concentrations but normal serum thyroxine and triiodothyronine concentrations, with few or no symptoms and signs of hyperthyroidism. These patients are said to have subclinical hyperthyroidism. Thyroid uptake of radioiodine may be measured to distinguish thyroiditis or excess thyroid hormone administration, in which the thyroid uptake is low, from other causes of hyperthyroidism, in which the thyroid uptake is high.

Treatment of hyperthyroidism

Hyperthyroidism is usually a chronic, even lifelong, disorder. It can be treated with an antithyroid drug, radioactive iodine, or surgery (thyroidectomy), in which a portion or all of the thyroid gland is surgically removed. There are three widely used antithyroid drugs—methimazole, carbimazole (which is rapidly converted to methimazole in the body), and propylthiouracil. These drugs block the production of thyroid hormone but have no permanent effect on either the thyroid gland or the underlying cause of the hyperthyroidism. Patients with hyperthyroidism caused by Graves disease are often treated with an antithyroid drug for one to two years in the hope that they will have a remission of the disease and remain well after the drug is stopped; this is successful in 30 to 50 percent of patients. Radioactive iodine is taken up by thyroid cells in the same way as is nonradioactive iodine, but the radiation destroys the cells, thereby reducing thyroid hormone production and also reducing the size of the thyroid gland. It is highly effective, but it results ultimately in hypothyroidism in most patients and, in some patients, may even lead to the later development of certain types of solid cancers (e.g., breast cancer). It is suitable for patients with Graves disease and is the preferred treatment for patients with a nodular goitre, in whom hyperthyroidism is a lifelong condition. The removal of the thyroid by thyroidectomy is rarely performed, except in the case of patients with a large goitre. When caused by thyroiditis, hyperthyroidism is transient, usually lasting only four to six weeks or at most two months. Most patients need no treatment or only symptomatic treatment with a beta-adrenergic antagonist drug (beta-blocker).

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Hyperthyroidism

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