Thyrotoxicosis is the term used to describe what happens when there are excess thyroid hormones in the body. People with thyrotoxicosis can also have a low level of thyroid-stimulating hormone (TSH) in the bloodstream.
Thyrotoxicosis is different than hyperthyroidism, which is associated with increased thyroid hormone and secretion from the thyroid gland. Thyrotoxicosis refers to actual physical and laboratory findings showing excess circulating thyroid hormones, regardless of the source.
Here is what you need to know about thyrotoxicosis, including types, symptoms, causes, diagnosis, and treatment.
Verywell / Laura Porter
Types of Thyrotoxicosis
The thyroid gland is the small, butterfly-shaped gland located on the front of the neck. This gland with the help of the two thyroid hormones—triiodothyronine (T3) and thyroxine (T4)—helps the thyroid to regulate metabolism, the process of converting food into energy.
The thyroid gland also plays a vital role in growth and development and in regulating vital body functions like heart rate and body temperature. When your thyroid can’t produce the right balance of hormones, that imbalance will upset the body.
The most common conditions that can lead to thyrotoxicosis are Graves’ disease, subacute thyroiditis, Plummer disease, and toxic adenoma.
Graves’ Disease
Graves’ disease is a type of thyrotoxicosis where the thyroid gland is hyper-functioning. Graves’ disease is also considered an autoimmune disorder that—because of inflammation—damages the thyroid.
Graves’ can affect anyone, but it seems to be more common in women and people ages 30 to 50. Additionally, the risk for Graves’ disease is higher if other members of your family have the condition. Having another autoimmune disease—like rheumatoid arthritis or lupus—may also increase your risk for Graves’ disease.
Subacute Thyroiditis
Subacute thyroiditis is an acute inflammatory disease of the thyroid gland. It often occurs after an upper respiratory infection or other viruses. In the first weeks of subacute thyroiditis, a person with the condition will experience signs of thyrotoxicosis, including enlargement and tenderness of the thyroid gland.
Pain from the thyroid gland may radiate into the jaw or ears. A person with this condition may also experience malaise (a general unwell feeling), a fever that could be as high as 104 F (40.0 C), and muscle and joint pain.
Subacute thyroiditis will cause other symptoms of thyrotoxicosis and it may increase your risk for another thyrotoxicosis condition later in life. And while subacute thyroiditis tends to be temporary, it can still cause some permanent complications if left untreated, including thyroid storm.
A thyroid storm is a life-threatening emergency where a person’s heart rate, blood pressure, and body temperature can quickly accelerate to very dangerous levels.
Plummer Disease
Plummer disease—also called toxic multinodular goiter—causes an enlarged thyroid gland, firm thyroid nodules (lumps), and overproduction of thyroid hormone. Risk factors for Plummer disease include being female and being over age 55. Most people with the condition will have the condition for many years before getting a formal diagnosis.
Iodine deficiency is another risk factor for Plummer disease although this type of deficiency tends to be uncommon in the United States. Iodine is an element needed for the production of thyroid hormone.
Symptoms of Plummer disease are similar to other types of thyrotoxicosis and may include heat intolerance, muscle weakness and twitching, severe fatigue, tremors, unintentional weight loss, and diarrhea.
Plummer disease may cause the thyroid gland to swell to the point that a person with the condition may have problems breathing or swallowing. Removal of the excess tissue in the thyroid gland may resolve breathing and swallowing problems related to Plummer disease.
Toxic Adenoma
Toxic adenoma causes an overactive thyroid when a single nodule grows on the thyroid gland making it enlarged and causing it to produce too much thyroid hormone.
It is very similar to Plummer disease except that it only causes one nodule in the gland. It will also cause similar symptoms and has the same causes and risk factors as Plummer disease.
Hashitoxicosis
Hashitoxicosis is the initial hyperthyroid phase of Hashimoto’s thyroiditis (also called Hashimoto’s disease), an autoimmune disease. Hashitoxicosis is temporary thyrotoxicosis that causes increased release of thyroid hormone resulting in destructive inflammation of the thyroid gland.
The signs and symptoms of hashitoxicosis are similar to other types of thyrotoxicosis and tend to be mild to moderate. Hashitoxicosis affects about 4.47% of people who eventually go on to develop Hashimoto’s thyroiditis.
Thyrotoxicosis Symptoms
The symptoms of thyrotoxicosis are caused by high levels of thyroid hormones in the blood increasing the metabolic rate. Metabolism or metabolic rate is the rate at which the body uses energy or burns calories.
Mild thyrotoxicosis usually doesn’t cause symptoms, but most people will start to experience symptoms once the condition becomes severe.
Once thyrotoxicosis is severe, you may experience:
- Diarrhea
- Extreme weight loss
- Increased or decreased appetite
- Shaking or tremors, especially in the hands
- Sweating
- Heart palpitations or an increased heart rate
- Anxiety or feelings of distress
- Mood changes
- Feeling hot even when others feel cold
- Hair thinning
- Swelling or nodules in the thyroid gland
- Skin problems, including redness and itching
People who have autoimmune thyrotoxicosis, such as Graves’ disease and Hashimoto thyroiditis, may also experience eye problems (i.e. eye-bulging, dryness, and swelling), swelling of the fingertips, and reddish thickening of the skin on the shins.
Thyrotoxicosis can affect menstruation and cause irregular periods. If thyrotoxicosis is severe, it can lead to fertility problems in people who menstruate.
Causes
The prevalence of thyrotoxicosis in the United States is around 1.3%. It is more common in women and the risk for thyrotoxicosis increases with age. Rates of thyrotoxicosis are higher in Whites compared to Hispanics and Blacks.
Genetic factors play a part in the development of thyrotoxicosis, especially in autoimmune thyrotoxicosis. Both Hashimoto’s thyroiditis and Graves’ disease affect multiple family members.
In areas where iodine deficiency is common, nodular thyroid disease (Plummer disease and toxic adenoma) accounts for as many as 50% of the cases. Age also plays a part and both types affect mostly older adults.
Other causes of thyrotoxicosis include struma ovarii, thyroiditis, thyroid treatments, and other medications.
- Struma ovarii is a rare type of ovarian tumor made of mainly thyroid tissues. In some cases, it will lead to thyrotoxicosis.
- Thyroiditis is when a virus or bacteria or a medication, like lithium (a mood stabilizer) causes the immune system to inflame the thyroid gland and the thyroid gland to release too much thyroid hormone into the bloodstream.
- Thyroid medications can sometimes be a cause of thyrotoxicosis. Your healthcare provider can reduce your dosage to minimize this problem. You may be able to prevent thyrotoxicosis in this case by regularly checking thyroid levels and getting ahead of any problems.
- Other prescription drugs, like Amiodarone—an antiarrhythmic drug, can stimulate the thyroid gland and cause overproduction of thyroid hormone or damage to the thyroid. That damage—much like inflammation—can cause excess hormone to release into the bloodstream.
If you have had thyroid issues in the past or a family history of thyroid disease, ask your healthcare provider if any of the medications you currently take might negatively affect your thyroid gland.
Diagnosis
A diagnosis of thyrotoxicosis and its causes is based on physical examination and symptom history, along with blood tests to measure thyroid hormone levels.
With the physical exam of the thyroid gland, your healthcare provider will examine your neck where the gland is located to look for enlargement and tenderness of the thyroid, and for any nodules or cysts.
They will want to know if you have problems with swallowing or experience frequent choking. Your healthcare provider will want to know about significant weight loss or gain, fatigue, heart palpitations, tremors, and other common symptoms of thyrotoxicosis.
If Graves’ disease is suspected, they will look for eye involvement which can be seen in up to 70% of people with the condition. You will also be asked about skin involvement, which is common in up to 4% of people with Graves’ disease.
Bloodwork for thyrotoxicosis will show raised thyroid levels, and suppressed TSH levels. If your healthcare provider suspects Graves’ disease or Hashimoto’s thyroiditis, they will request additional blood work to check for thyroid antibodies. Doing a thyroid uptake scan to look at activity of the gland can help differentiate between the potential diagnoses.
Treatment
Thyrotoxicosis cannot be prevented, but it is treatable. There are three main approaches to treating thyrotoxicosis—medication, radioactive iodine, and surgery.
Medication
Drugs called beta blockers, such as propranolol can be used to treat some symptoms of thyrotoxicosis, such as heart rate, anxiety, and sweating. Other drugs, including carbimazole and propylthiouracil, are also used to act upon thyroid gland proteins to prevent overproduction of thyroid hormone.
Radioactive Iodine
If your healthcare provider prescribes radioactive iodine, this involves you taking a capsule of radioactive iodine. The iodine will be taken up by the thyroid gland where it becomes concentrated and causes gradual destruction of the overactive gland.
A single dose of radioactive iodine can reduce the amount of thyroid hormone produced by the gland for up to 80% to 90% of people.
Surgery
Sometimes, a treating healthcare provider will recommend removing all or part of the thyroid gland. A subtotal thyroidectomy involves the removal of a small part of the thyroid to preserve thyroid function. With a total thyroidectomy, the entire thyroid gland is removed.
A thyroidectomy—regardless of the type—can only be done after thyroid levels have become stabilized with medication.
Thyroidectomies are only done in special circumstances, such as:
- In people who have exceptionally large goiters (abnormal enlargement of the thyroid gland)
- For people who refuse or cannot do radioactive iodine therapy
- Children with severe thyroid disease
- People who need thyroid function normalized quickly, such as a patient with an unstable cardiac condition
- For serious cases of Plummer disease or toxic adenoma
- Thyroid cancer
The literature on thyroidectomies shows that both subtotal and total thyroidectomy can bring about favorable results. And the research on total thyroidectomies shows a 100% cure rate.
After a thyroidectomy, most people will experience a sore throat and hoarseness that can last for several weeks. If the thyroid gland has completely been removed, you will need thyroid hormone replacement therapy every day for the rest of your life to replace what your body no longer produces naturally.
Your healthcare provider will also want you to have regular checkups and bloodwork to monitor thyroid levels from medication therapies.
In some cases, as can be the case with thyroiditis, you may not need any treatment at all. Thyrotoxicosis could go away on its own, but this is extremely rare. Most people will need some type of treatment to manage disease symptoms.
Complications
Left untreated, thyrotoxicosis can lead to serious medical problems. And while these complications can be scary, they are preventable and treatable.
The most serious complication is a thyroid storm. Untreated thyrotoxicosis can also cause problems for your bones and heart.
Thyroid storm: If you or a loved one develop severe symptoms of a thyroid storm, such as shock and delirium, call 911 or get to a nearby emergency room. Thyroid storm also causes severe abdominal pain, fever, and decreased mental clarity and alertness.
Bone loss and osteoporosis: Research shows excess thyroid hormone can lead to bone cell turnover. This can increase the risk of osteoporosis because of the reduction in the stability and strength of bones.
Heart issues: Excess thyroid hormone can cause an enlarged heart as well as blood pressure changes. Enlargement is due to the heart tissues being stimulated by excess thyroid hormone, and an enlarged heart increases your risk for heart disease, arrhythmia, and heart failure.
You should call 911 or head to a local emergency room, if you feel extremely tired, have a fast heartbeat, chest pain, or difficulty with breathing. These symptoms are an indication something might be wrong with your heart.
A Word From Verywell
Thyrotoxicosis can be a serious medical problem, but it is treatable. Even with Graves’ disease that gets worse with time, treatment can manage symptoms and improve quality of life.
Call your medical provider if you experience symptoms of thyrotoxicosis and let them know if you have risk factors for thyroid disease.
If you are ultimately diagnosed with thyrotoxicosis, your healthcare team will do everything to find out the cause and work to reduce and prevent damage caused by excess thyroid hormone. With this approach, you can avoid long-term consequences of thyrotoxicosis and continue to enjoy a good quality of life.
