Introduction

The thyroid gland is one of the endocrine (hormone) glands in the body. These glands make hormones to regulate many different functions in the body. An overactive thyroid produces too many hormones. This problem is also known as hyperthyroidism. The most common cause is Graves' disease.

If too many hormones are made, the body’s metabolism goes into overdrive. This can lead to noticeable symptoms such as weight loss, sweating, nervousness or a rapid heartbeat. An overactive thyroid also increases the risk of cardiovascular disease (problems affecting the heart and/or blood vessels).

If the thyroid gland doesn’t produce enough hormones, the body’s metabolism slows down.

At a glance

• An overactive thyroid occurs if the thyroid gland makes too many hormones.
• This can lead to various problems, including nervousness, weight loss, a rapid heartbeat and an enlarged thyroid gland.
• An overactive thyroid is more common in women than in men.
• It is usually treated with tablets.
• If this treatment isn’t enough, other possible options are surgery or radioiodine therapy.

Symptoms

Hyperthyroidism often causes the thyroid gland, which is located at the front of the neck, to become noticeably larger. A swollen thyroid is called a goiter. The whole gland isn’t always swollen. A lump (nodule) may be felt or seen instead. But some people have an overactive thyroid without a goiter or thyroid nodules – and either of those can have other causes.

Normal thyroid (left) and thyroid gland that is making too many hormones (right)

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A swelling in your neck may be a sign of thyroid disease, such as an overactive thyroid, iodine deficiency or thyroid nodules.

If there are too many thyroid hormones in your blood, various chemical reactions and functions in the body get out of balance. This can cause symptoms such as

• A pounding heart (palpitations) and rapid heartbeat, and sometimes an irregular heartbeat too
• High blood pressure
• Weight loss despite an increased appetite
• Diarrhea
• Trembling, nervous restlessness, irritability, sleep problems
• Weakness and tiredness

People who have an overactive thyroid often sweat a lot and feel uncomfortable when they are warm. Their skin is often warm and moist to the touch, and they may have thinning hair.

If it is caused by Graves’ disease, bulging eyes and vision problems can also occur.

Possible symptoms of an overactive thyroid

Causes

The most common cause of an overactive thyroid gland is Graves’ disease. In this condition, a problem with the immune system causes the thyroid gland to make more thyroid hormones than normal.

Hyperthyroidism may also arise if thyroid gland cells start producing hormones “autonomously” – in other words, without being “told” to. The activity of the thyroid gland is usually regulated by the pituitary gland. It constantly monitors whether the right amount of thyroid hormones is being produced and can then help make adjustments as needed. Sometimes, though, the thyroid gland cells no longer react to signals from the pituitary gland. As a result, the thyroid gland may produce far more hormones than are actually needed. The autonomous cells are sometimes found in the whole thyroid gland, and sometimes they are only found in one or several benign (non-cancerous) growths called nodules. These growths are also known as “hot” nodules.

Sometimes too many thyroid hormones get into the blood if the thyroid gland is inflamed. Thyroid hormones that are stored in the inflamed tissue are then released, temporarily leading to symptoms similar to those caused by an overactive thyroid.

High thyroid hormone levels are only very rarely caused by malignant (cancerous) thyroid tumors.

Prevalence

About 1 out of 100 people have an overactive thyroid. It is more common in women than in men, and usually develops in middle age.

Effects

If people who have an overactive thyroid don’t get proper treatment, they may develop cardiovascular diseases such as atrial fibrillation (an irregular heartbeat). Because their old bone tissue is broken down and new bone tissue is formed at a faster rate, osteoporosis may develop over the long term.

In rare cases, an overactive thyroid leads to a potentially life-threatening situation known as a thyrotoxic crisis or a “thyroid storm.” This can be triggered by iodine-containing medication or an x-ray contrast medium (a dye-like substance), for example. As well as the typical symptoms of an overactive thyroid, it can cause a high fever, vomiting, restlessness and anxiety, an irregular heartbeat, confusion and drowsiness, and sometimes even a coma or cardiovascular collapse (where not enough blood flows around the body). A thyroid storm is a medical emergency, requiring hospital treatment in an intensive care unit.

Diagnosis

If it is thought that you may have an overactive thyroid, the doctor will first ask you a few questions and then feel your thyroid gland from the outside by touching your neck. This allows them to see whether the gland is bigger than usual or has any nodules in it.

Blood tests can provide important information about the cause, including whether the excessive production of thyroid hormones is due to a problem with the thyroid gland itself or whether it is being caused by a problem with the pituitary gland. Signs of Graves' disease can also be detected in a blood test.

Ultrasound examinations allow doctors to take a closer look at the thyroid gland tissue and any nodules in the gland. An examination known as a thyroid scan (or thyroid scintigraphy) can be done to see whether a nodule is producing too many hormones (a “hot” nodule) or whether it is inactive (a “cold” nodule).

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Various tests can be used to diagnose an overactive thyroid and to find its cause. The information “Understanding thyroid tests” explains them all briefly.

Treatment

Mild hyperthyroidism sometimes gets better without treatment. But the overproduction of thyroid hormones is usually first stopped using tablets called anti-thyroid drugs. The hyperthyroidism can come back when you stop using the anti-thyroid drugs, though. If that happens, the thyroid is first treated again with these anti-thyroid drugs to “calm” it down, and then either surgery or radioactive iodine is used.

If a single thyroid nodule is causing the hyperthyroidism, then one procedure to cut out the nodule may be enough. Otherwise, the entire gland can be surgically removed. Sometimes a small part of the thyroid tissue is left in the body so that it can continue to produce hormones.

Radioiodine therapy involves swallowing radioactive iodine that is absorbed by the thyroid gland and destroys the cells that are making too many hormones. This treatment is often considered if surgery isn’t possible or if you don't want to have it.

Further information

When people are ill or need medical advice, they usually go to see their family doctor first. Information about health care in Germany can help you to navigate the German health care system and find a suitable doctor. You can use this list of questions to prepare for your appointment.

Sources

• Bartalena L, Kahaly GJ, Baldeschi L et al. The 2021 European Group on Graves' orbitopathy (EUGOGO) clinical practice guidelines for the medical management of Graves' orbitopathy. Eur J Endocrinol 2021; 185(4): G43-G67. [PubMed: 34297684]
• De Leo S, Lee SY, Braverman LE. Hyperthyroidism. Lancet 2016; 388(10047): 906-918. [PMC free article: PMC5014602] [PubMed: 27038492]
• Deutsche Gesellschaft für Nuklearmedizin (DGN). Radioiodtherapie bei benignen Schilddrüsenerkrankungen (Version 5). DGN-Handlungsempfehlung (S1 Leitlinie). AWMF-Registernr.: 031-003. 2015.
• Jameson JL, Mandel SJ, Weetmann AP. Disorders of the Thyreoid Gland. In: D. L. Kaspers, S. L. Hauser, J. L. Jameson et al. (Ed). Harrison's Principles of Internal Medicine. McGraw-Hill Education; 2015.
• Kahaly GJ, Bartalena L, Hegedüs L et al. 2018 European Thyroid Association Guideline for the Management of Graves’ Hyperthyroidism. Eur Thyroid J 2018; 7(4): 167-186. [PMC free article: PMC6140607] [PubMed: 30283735]
• National Institute for Health and Care Excellence (NICE). Thyroid disease: assessment and management (NICE Guidelines; Band NG145). 2019.
• Ross DS, Burch HB, Cooper DS et al. 2016 American Thyroid Association Guidelines for Diagnosis and Management of Hyperthyroidism and Other Causes of Thyrotoxicosis. Thyroid 2016; 26(10): 1343-1421. [PubMed: 27521067]
• Viszeralchirurgie DGfA-u, (DGAV). S2k-Leitlinie Operative Behandlung benigner Schilddrüsenerkrankungen. 2021.

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