Overview

Thyrotoxicosis is a clinical condition characterised by too much circulating and in tissue thyroid hormone. This means that the thyroid hormone is excessively produced by the thyroid gland.¹ The thyroid hormone controls the body’s vital functions, including metabolism, body temperature and heart rate. Too much thyroid hormone in the body can mean that your metabolism becomes too fast, potentially leading to severe complications.

Thyrotoxicosis has a wide range of symptoms and causes, although the most common cause is an overactive thyroid gland. If left untreated, it can lead to adverse health complications. In very severe cases, the condition can become life-threatening, referred to as a ‘thyroid storm’.²

There are several treatment options available for thyrotoxicosis. It’s crucial to develop a personalised plan for its treatment and management, dependent on the underlying cause and clinical symptoms. When treated properly, thyrotoxicosis can be effectively managed, preventing further health complications.

Understanding thyrotoxicosis 

Thyrotoxicosis is defined by abnormally high levels of thyroid hormone in the bloodstream. This increases your body’s metabolism, the process by which your body transforms food into energy. Increased metabolic rate can lead to a range of symptoms which can affect the whole body.

Thyrotoxicosis is sometimes referred to as hyperthyroidism, however, these are not the same condition. Hyperthyroidism is defined by increased thyroid hormone synthesis and production from the thyroid gland, whereas thyrotoxicosis refers to the clinical syndrome of elevated thyroid hormone levels, irrespective of the underlying cause.

Symptoms of thyrotoxicosis vary significantly and are generally mild in most cases, although they can become more intense in severe cases. Common symptoms include unexplained weight loss, irregular heartbeat (arrhythmia) and rapid heartbeat (tachycardia). The condition can also lead to feelings of anxiety, shakiness or irritability. In many cases, individuals affected by thyrotoxicosis experience increased sensitivity to heat. These symptoms can present a significant physical and emotional impact on daily life.

It is critical to determine the underlying cause of thyrotoxicosis to find an appropriate treatment strategy. The most common cause of the condition is hyperthyroidism, which is typically caused by Grave’s disease and overactive thyroid nodules. Grave’s disease is an autoimmune disorder which results in excess secretion of thyroid hormones.³

Thyroid inflammation, also known as thyroiditis, can also lead to thyrotoxicosis. This can be triggered by infections, immune system disorders and certain medications which cause thyroid swelling. Further causes of thyrotoxicosis include taking too much thyroid medication, such as levothyroxine, which is used to treat hypothyroidism. Excessive thyroid hormone consumption from beef contaminated with thyroid tissue is a very rare cause of thyrotoxicosis.

Risk factors for thyrotoxicosis include having a family history of the condition, being assigned female at birth, being over the age of 60 and having recently delivered a baby. These factors increase your chances of developing thyrotoxicosis.

Determining the underpinning cause of thyrotoxicosis is critical when planning the best treatment strategy.

Clinical diagnosis of thyrotoxicosis 

Thyrotoxicosis can be diagnosed using blood tests, which show elevated thyroid hormone levels, including triiodothyronine (T3) and thyroxine (T4), as well as low levels of TSH. Additionally, antibody tests are used to check if Graves’ disease is the underlying cause of the condition.

You will usually be referred to an endocrinologist, a doctor who specialises in diagnosing and treating conditions related to the hormone system. Your healthcare provider will also perform a physical exam to check for symptoms such as rapid heart rate, shakiness and an enlarged thyroid. Imaging tests are commonly used as a diagnostic tool, such as a thyroid ultrasound and thyroid scan.¹ These tests assess inflammation and determine if there are nodules on the thyroid. Providing an accurate diagnosis of thyrotoxicosis is essential to inform prognosis and develop a treatment plan.

Management and treatment strategies

There are several treatment options, dependent on the underlying cause, which help people living with thyrotoxicosis to effectively manage the condition.⁹ Following diagnosis, your healthcare provider will recommend a treatment plan which is best suited to your needs. This article discusses typical thyrotoxicosis treatments, including anti-thyroid medications, radioactive iodine therapy and surgical treatment.

Medical management 

Anti-thyroid medications, such as methimazole and propylthiouracil, are common first-line strategies for treating thyrotoxicosis.⁴ These work to decrease circulating thyroid hormone levels by blocking your thyroid from producing hormones. Antithyroid drugs (ATDs) are often used for long-term treatment when Graves’ disease is the underlying cause. ATDs may also be used short-term to prepare for radioactive iodine therapy or surgery. They cannot be used to treat a thyroid storm in severe cases, which must be treated in a hospital.^2,5

Alternative medications include corticosteroids, which help to reduce inflammation and pain if you have thyroiditis. Additionally, beta-blockers can be used for short-term relief of physical symptoms associated with thyrotoxicosis, such as rapid heartbeat and shakiness. Regular checkups are important to monitor treatment response and ensure that your medication is working effectively.

Radioactive iodine therapy

Radioactive iodine (RAI) therapy is a safe and effective treatment for thyrotoxicosis as well as thyroid cancers. It works by specifically targeting and destroying overactive thyroid cells, reducing thyroid hormone levels in the body. 

RAI therapy is usually recommended when antithyroid drugs have been unsuccessful in treating thyrotoxicosis, you are unable to take them, or when surgical treatment is too risky based on different health factors. Adverse effects of RAI therapy are rare and not fully confirmed.⁶ It is important to note that RAI therapy is not safe for pregnancy or breastfeeding.

There are several steps involved in preparing for RAI therapy. Firstly, blood tests will be done to monitor your thyroid levels, and antithyroid drugs should be stopped at least a week before the procedure. It is also recommended to follow a low-iodine diet in the weeks leading up to the procedure. Injections of thyroid-stimulating hormone (TSH) will be provided to increase the amount of radioactive iodine your thyroid will absorb, making the procedure more effective.

Since this treatment permanently destroys the thyroid, people who receive this therapy must take thyroid hormone treatment for the rest of their lives to maintain normal thyroid levels.

Surgical treatment (thyroidectomy)

In some cases, the thyroid gland may need to be removed during surgery, known as a thyroidectomy. This is a highly effective treatment for thyrotoxicosis, particularly when caused by Graves’ disease. It is recommended in cases where RAI therapy has been unsuccessful. Thyroidectomy is a highly safe treatment option, and surgical complications are rare, affecting 1-3% of patients.⁷ To prepare leading up to your surgery, ATDs are usually prescribed to reduce the risk of thyroid storm, and beta-blockers are prescribed to manage symptoms.

Following surgery, most patients can go home on the same day or the next day, and it takes about 2-3 weeks for a full recovery. Your healthcare provider will give you instructions about post-operative care, such as keeping the head elevated while sleeping, limiting intense physical activity and monitoring for signs of complications.

Although thyroidectomy is a successful treatment, it causes long-term hypothyroidism, meaning that people who have undergone this surgery must take thyroid hormone treatment for the rest of their lives.

Special considerations

There are several considerations which should be taken into account in the treatment and management of thyrotoxicosis. The condition may cause complications during pregnancy, however, there are safe treatment options available if you are pregnant or breastfeeding.⁸

Radioactive iodine therapy is not a recommended treatment if you are pregnant since radioiodine can pass through the placenta and negatively affect fetal development. This treatment will also not be recommended if you are breastfeeding or have severe thyrotoxicosis. Thyroidectomy is generally not recommended if you are pregnant unless it is absolutely necessary.⁹

Alternatively, a low dose of antithyroid drugs can be prescribed to reduce the likelihood of the fetus being affected. If you are taking ATDs, there is a very slight increased risk of the baby having developmental abnormalities, so some patients choose to have permanent treatment with RAI therapy or surgery to allow them to have a pregnancy without needing to take antithyroid drugs.

Follow-up and long-term management

Clinical follow-ups are essential to monitor your treatment response and any possible side effects. Frequent check-ups, which assess your circulating thyroid hormone levels, are useful to check for hypothyroidism and ensure that your treatment is working effectively.

It is important to follow your recommended treatment plan to prevent health complications, including thyroid storm. This may be triggered if you are taking antithyroid drugs and suddenly stop taking them.¹⁰

Following thyroidectomy, thyroid replacement hormone (levothyroxine) should be started, and TSH concentration monitored 6–8 weeks after surgery. Similarly, following RAI therapy, levothyroxine should be taken long-term to replace the thyroid hormone your thyroid gland normally makes.⁹

Follow-up care is a key part of your treatment and safety. After your thyroid surgery, it is important to follow a post-operative care plan. This includes getting plenty of rest, taking daily walks if possible, avoiding strenuous physical activity and heavy lifting for at least 3 weeks post-surgery. It’s also recommended not to over-extend your neck for 2 weeks post-surgery. It may be painful to swallow and eat after your thyroidectomy. It is recommended to try soft foods and cold drinks to avoid discomfort when eating.

You may also take pain medications during your treatment and recovery as directed by your healthcare provider.

Summary

Thyrotoxicosis is a treatable condition which is defined by having too much thyroid hormone in your body. An overactive thyroid gland, referred to as hyperthyroidism, is the most common cause of thyrotoxicosis. However, there are several causes of elevated thyroid hormone levels, such as thyroiditis, excess thyroid medication and consuming excess thyroid hormone in your diet. It is essential to determine the underlying cause of thyrotoxicosis to find a treatment strategy which is best suited to your needs.¹⁰

Thyrotoxicosis is a manageable condition with various effective treatment options available. 

When left untreated, it can lead to several health complications such as atrial fibrillation, congestive heart failure and ischemic stroke. In rare cases, thyrotoxicosis can lead to thyroid storm, which is a life-threatening condition.²

The most commonly used treatment is antithyroid medications, which are prescribed to block your thyroid from producing hormones. Alternative treatments include corticosteroids, radioactive iodine therapy and thyroid surgery. Pain medications and beta blockers may also be recommended to manage your thyrotoxicosis symptoms. It is important to develop a personalised treatment plan which best suits your specific needs. If you need to be treated through surgery, following your post-operative care plan will help you recover safely within a few weeks. Clinical follow-ups are essential to monitor your treatment response and get your body back into balance.