Thyrotoxicosis

What is Thyrotoxicosis?

Thyrotoxicosis is a medical condition where there are excessively high levels of thyroid hormones, called T3 and/or T4, in the body. This condition can come from various causes. It is sometimes inaccurately referred to as hyperthyroidism, which is actually a type of thyrotoxicosis where the body is producing too much thyroid hormone.

The symptoms of thyrotoxicosis vary widely. In some people, it might not cause any symptoms or lead to very mild symptoms. However, in severe cases, it can be life-threatening. Typical symptoms are the result of the body’s metabolism increasing due to the excess thyroid hormones. These symptoms can include weight loss, intolerance to heat, and heart palpitations.

Diagnosing thyrotoxicosis can be challenging because it shares symptoms with many other conditions. Diagnosing it usually involves an extensive physical exam, laboratory tests, and imaging studies. If thyrotoxicosis is not treated properly, it could lead to serious complications. These can include loss of mental clarity, weak bones (osteoporosis), muscle weakness, irregular heartbeat (atrial fibrillation), heart failure, blood clots, heart-related collapses, and even death.

What Causes Thyrotoxicosis?

Thyrotoxicosis, a condition characterized by an overactive thyroid, can stem from two basic sources: a natural (endogenous) cause, or an external (exogenous) source.

The body’s thyroid hormone may be naturally overproduced in certain conditions:

* Graves’ disease
* Goiter with multiple nodules (also known as toxic multinodular goiter)
* Benign lumps in the thyroid (toxic adenoma)
* Certain types of pituitary gland tumors
* Hyperthyroidism induced by high levels of human Chorionic Gonadotropin (HCG)
* Inflammation of the thyroid gland (thyroiditis)
* Certain medications

An external source of thyroid hormone could be:

* Deliberately taking too much thyroid hormone (factitious hyperthyroidism)
* Taking too much thyroid hormone medication

Graves’ disease is the most common cause of thyrotoxicosis, followed by multinodular goiter and adenoma. Other reasons include different types of thyroiditis, hyperthyroidism during pregnancy, and thyrotoxicosis induced by certain drugs like amiodarone and iodinated contrast.

Less common causes of thyrotoxicosis include certain pituitary gland tumors, ovarian tumors with thyroid tissue (struma ovarii), gestational trophoblastic disease (a rare pregnancy complication), deliberately taking too much thyroid medicine, genetic mutations activating the TSH (thyroid-stimulating hormone) receptor, and metastases or spread of functional thyroid cancer.

Risk Factors and Frequency for Thyrotoxicosis

Thyrotoxicosis, a condition where the body has unbalanced levels of thyroid hormones, affects 1.2% of people in the United States. This number includes both overt and subclinical thyrotoxicosis, which affect 0.5% and 0.7% of the population respectively. People between the age of 20 and 50 are the most likely to experience thyrotoxicosis.

• The most common cause of thyrotoxicosis is Graves’ disease. This condition is responsible for 20 to 50 per 100,000 cases.
• Graves’ disease mainly affects women aged 30 to 50, but it can happen to anyone, regardless of age or gender. For every 5 women diagnosed, 1 man is diagnosed.
• Other causes of thyrotoxicosis include toxic multinodular goiter and toxic adenoma. The number of people suffering from toxic nodular goiter tends to increase with age and in places where dietary iodine is deficient.
• About 10% of thyrotoxicosis cases are caused by thyroiditis, which is inflammation of the thyroid gland.
• Finally, 1% to 2% of patients with thyrotoxicosis might develop a severe complication called thyroid storm.

Signs and Symptoms of Thyrotoxicosis

Thyrotoxicosis is a medical condition in which there’s an excessive amount of thyroid hormone in the body. This can cause various signs and symptoms. The most common symptoms include weight loss even while appetite is normal or increased, difficulty dealing with higher temperatures, a lot of sweating, heart palpitations, shaking, anxiety, weak muscles close to the body, hair loss, and getting tired easily. Other signs include rapid heart beat and irregular heartbeat, particularly seen in older patients or those with other heart conditions. Women might have irregular or missed periods while men may, in rare cases, develop enlarged breast tissue. It’s also worth mentioning that older patients might not show many typical symptoms but present with depression, fatigue, and weight loss. This is known as apathetic thyrotoxicosis.

When these patients are examined, they often appear underweight, a bit feverish, sweaty, and anxious. Physical indications might include an enlarged thyroid gland (goiter), rapid or irregular heartbeat, shortness of breath, tenderness in the stomach area, hyperactive reflexes, weak muscles close to the body, shaking, and possibly enlarged male breasts. Patients suffering from Graves’ disease, a specific type of thyrotoxicosis, may have additional symptoms like appearance changes in the legs (pretibial myxoedema), bone abnormalities (thyroid acropachy), and abnormal nails.

Some less common but severe symptom presentations include thyroid storm which is characterized by rapid heart beat, fever, altered mental status, restlessness, symptoms of heart failure, and impaired liver function. Some symptoms are unique to the type of thyrotoxicosis. For instance, in Graves’ disease, eye problems are common, including bulging eyes, swollen eyelids, red eyes, and changes in vision while other patients might have thickening and redness of the skin on the lower legs and bone abnormalities.

In another type of thyrotoxicosis called subacute thyroiditis, usually following an upper respiratory illness, patients may complain of fever, neck pain and swelling along with a firm and tender thyroid gland. In painless thyroiditis, usually presenting after childbirth, personal or family history of autoimmune or thyroid disease is common. Suppurative thyroiditis is another form marked by a painful, red lump in the front of the neck and patients often complain of fever, difficulty swallowing, and hoarseness.

In rare instances, a patient can present with weak muscles and low blood potassium levels, a condition known as thyrotoxic periodic paralysis.

Testing for Thyrotoxicosis

If your doctor suspects a thyroid disorder, they may order tests for thyroid-stimulating hormone (TSH), thyroxine (T4), and triiodothyronine (T3) in your blood. If your TSH level is low and your T4 and T3 levels are high, this could mean that you have hyperthyroidism. Hyperthyroidism is a condition where your thyroid produces too many hormones. T3 levels often rise before T4 levels do. If your TSH level is normal or even high but your T4 and T3 levels are also high, the cause of your hyperthyroidism might be a problem with your pituitary gland.

To diagnose Graves’ disease, your doctor may test for antibodies (types of proteins used by your immune system) to the TSH receptor. If these antibodies are found in your blood, it’s a strong sign you have the disease. Graves’ disease is a specific type of hyperthyroidism. Thyroid peroxidase antibodies are also used in diagnosing Graves’ disease, but they are present in only about 75% of cases.

Radioactive iodine uptake studies or thyroid scans can be helpful in figuring out what’s causing an overactive thyroid, especially if the doctor doesn’t think it’s Graves’ disease. In Graves’ disease, the radioactive iodine spreads out evenly in the thyroid, unless the person also has nodules or fibrosis. If the thyroid has one toxic adenoma (a benign tumor) or several (toxic multinodular goiter), the radioactive iodine will concentrate more in these areas. Patients with thyroiditis (inflammation of the thyroid), ingestion of thyroid hormone, or recent exposure to excess iodine will take up almost no radioactive iodine.

In cases of thyroiditis (an inflammation of the thyroid), inflammatory markers such as erythrocyte sedimentation rate and C-reactive protein are usually elevated. For pregnant women, doctors should check free T3 and T4, or total T3 and T4 along with serum TSH levels, adjusting for pregnancy. TSH levels might be lower than usual during the first half of pregnancy, but T4 should stay within normal range. If man-made (factitious) hyperthyroidism is suspected, thyroglobulin levels will be lower, and radioactive iodine uptake will also be less because the thyroid is being suppressed by the extra thyroid hormone that has been ingested.

Treatment Options for Thyrotoxicosis

The treatment of thyrotoxicosis, a condition where your thyroid gland produces excessive thyroid hormones, depends on what’s causing it. Often, you’ll be given medications like beta-blockers, such as propranolol, to help with symptoms like sweating, anxiety, and rapid heartbeat. The main treatment options are medicines known as thionamides, using a substance called radioiodine, and surgical removal of the thyroid.

Thionamides include drugs like propylthiouracil (PTU) and methimazole, and they work by reducing the thyroid gland’s hormone production. In Graves’ disease, a common cause of thyrotoxicosis, methimazole is often used, and once the patient’s hormone levels normalize, you can either continue the same drug dosage and add an artificial thyroid hormone or adjust the drug dosage to maintain a balanced level of hormone.

Thanks to thionamides, around half of all Graves’ disease patients achieve long-term remission. However, one downside is that symptoms might return after you stop taking the drug. Also, regarding methimazole, note that it usually works better and has fewer side effects, but it may lead to liver toxicity. Other possible side effects include itchiness, joint pain, and stomach upset.

Radioiodine therapy, where you consume a pill containing radioactive iodine, is another common treatment. The iodine is absorbed by the thyroid, which causes it to become inflamed and eventually stop working properly. This usually leads to a condition called hypothyroidism, which means you’ll need to take thyroid hormones for life. However, one small risk is thyrotoxicosis getting worse shortly after the treatment due to an excessive release of hormones.

Surgery to remove part or all of your thyroid can also treat thyrotoxicosis. While this is usually effective, it is also invasive and can lead to permanent hypothyroidism, necessitating life-long hormone treatment. Some potential complications include low calcium levels and voice changes due to nerve damage.

For thyroiditis, a condition where your thyroid is inflamed, treatment mainly involves symptom management because antithyroid drugs don’t usually work. This can include taking beta-blockers or anti-inflammatory medications.

Children, pregnant women, and the elderly also have specific treatment recommendations. For children, the first-line treatment is often methimazole therapy for a couple of years, but radioiodine therapy and surgery can also be options. However, radioactive iodine and a specific thyroid drug, PTU, aren’t recommended for very young children due to potential side effects. Pregnant women are usually treated with thionamides, but the dosage should be carefully adjusted. During the first trimester, PTU is preferred because methimazole carries a risk of birth defects.

What else can Thyrotoxicosis be?

Most people who have an overactive thyroid gland, also known as hyperthyroidism, often experience fatigue, palpitations, weight loss, excessive sweating, and intolerance to heat. Although these patients can typically be examined as outpatients, a thorough medical history taking, physical exam, and further laboratory tests and screenings are usually necessary to diagnose the underlying cause of their symptoms.

There are several causes of hyperthyroidism, divided into three main types:

• Primary Hyperthyroidism, which can be caused by:
  • Grave’s disease
  • Toxic multinodular goiter
  • Toxic adenoma
  • Metastases from follicular thyroid carcinoma
  • Struma ovarii
  • Excessive iodine in the body
  • Mutations causing the overactive TSH receptor
• Secondary Hyperthyroidism, which can result from:
  • A TSH-secreting pituitary adenoma
  • Chronic gonadotrophic-secreting tumors or pregnancy causing increased HCG levels
  • Gestational thyrotoxicosis
• Thyrotoxicosis without Hyperthyroidism, which can occur due to:
  • Thyroiditis, including Acute, subacute, and painless types
  • Certain drugs including Amiodarone, lithium, interferon-alpha, immune checkpoint inhibitors
  • Radiation exposure
  • Thyrotoxicosis factitia, which is due to the consumption of exogenous thyroid hormone (like supplements) or consumption of thyroid tissue (for example, in contaminated ground meat)

What to expect with Thyrotoxicosis

Generally, the outlook for thyrotoxicosis, also known as an overactive thyroid, is good when treated with the right medication.

Possible Complications When Diagnosed with Thyrotoxicosis

: Not treating or failing to diagnose an overactive thyroid, or thyrotoxicosis, can escalate into a severe condition called a thyroid storm. Symptoms of a thyroid storm include rapid heartbeat, fever, confusion, restlessness, signs of heart failure, and problems with liver function. It’s important for the doctor to know your full medical history to identify potential triggers like severe stress, illness, or a recent injury.

Treatments often involve using drugs such as methimazole or PTU to prevent the production of new thyroid hormones, and iodine to stop the release of existing hormones. Patients are also typically given beta-blockers and fluids to help manage symptoms, especially in a critical care environment.

Certain conditions can present similarly to a severe case of thyrotoxicosis or a thyroid storm. These include:

• Neurological or mental health conditions: anxiety attacks, psychosis, meningitis
• Heart-related conditions: valve diseases, irregular heart rhythms – like atrial flutter and fibrillation, and severe heart failure
• Gastrointestinal issues: acute liver failure, dehydration from a stomach bug
• Endocrine disorders: adrenal crisis, pheochromocytoma (a rare tumor of adrenal gland tissue)
• Infections: severe infection leading to shock
• Other related issues: overdose from certain types of medication, imbalance in electrolyte levels

Preventing Thyrotoxicosis

Patients should be informed about their health condition and why it’s important to follow the medication plan and regularly visit the clinic for check-ups. This helps to keep track of the condition and see if it’s getting worse.