The thyroid is a small, butterfly-shaped gland located at the base of the neck. It produces hormones that regulate metabolism, growth, and development. In some cases, the immune system mistakenly identifies the thyroid as a threat and begins attacking it. This is known as an autoimmune thyroid disease.
The most common autoimmune thyroid diseases are Hashimoto’s thyroiditis and Graves’ disease. In Hashimoto’s, the immune system makes antibodies that damage the thyroid gland and reduce hormone production. This typically leads to hypothyroidism, or an underactive thyroid. In Graves’ disease, the immune system makes antibodies that overstimulate the thyroid, causing hyperthyroidism or an overactive thyroid.
Autoimmune thyroid diseases are quite common, affecting around 5% of the population. They are more prevalent in women and seem to run in families. The exact reason why the immune system begins attacking the thyroid is not fully understood, but likely involves a combination of genetic and environmental factors.
What causes autoimmune thyroid disease?
Researchers believe there are several potential triggers that can lead the immune system to mistake the thyroid as harmful and initiate an attack:
Genetics
Genes play an important role. People with a family history of thyroid disease or other autoimmune disorders are at increased risk. Certain genes are associated with making antibodies that target the thyroid.
Sex hormones
Women are 5-10 times more likely to develop autoimmune thyroid diseases. Fluctuations in estrogen and progesterone may influence the immune response. The onset also frequently occurs after pregnancy.
Iodine
Consuming high amounts of iodine may trigger thyroid autoimmunity in those predisposed. The thyroid needs iodine to make hormones, but too much can cause inflammation.
Infections
Viral and bacterial infections are thought to initiate thyroid autoimmunity in some cases. The infection may change proteins in the thyroid, causing the immune system to mistake them as foreign.
Medications
Certain medications like interferon-alpha and interleukin-2 used to treat hepatitis, cancer, and kidney disease can trigger thyroid autoantibodies.
Radiation exposure
Radiation treatment to the neck area for medical purposes increases the risk of developing Hashimoto’s thyroiditis.
Smoking
Cigarette smoking is linked to a higher risk of Graves’ disease and an increase in thyroid antibodies.
Stress
Severe emotional or physical stress may initiate thyroid autoimmunity through effects on the immune system.
What are the signs and symptoms?
The symptoms of autoimmune thyroid disease depend on whether it leads to hypothyroidism or hyperthyroidism:
Hypothyroidism symptoms
- Fatigue
- Weakness
- Weight gain
- Depression
- Dry skin and hair
- Constipation
- Muscle cramps
- Heavy periods
Hyperthyroidism symptoms
- Anxiety/irritability
- Trouble sleeping
- Weight loss
- Racing heart
- Trembling hands
- Sweating
- Diarrhea
- Muscle weakness
How is autoimmune thyroiditis diagnosed?
If an autoimmune thyroid problem is suspected based on symptoms, a doctor will check for the following:
Thyroid antibodies
A blood test can detect elevated levels of antibodies like thyroid peroxidase (TPO) antibodies or thyroglobulin antibodies. These are markers of autoimmune thyroid disease. Hashimoto’s is associated with high TPO antibodies.
TSH levels
The main thyroid hormone regulation is through TSH (thyroid stimulating hormone). High TSH indicates hypothyroidism, while low levels indicate hyperthyroidism.
Thyroid ultrasound
This imaging test can detect inflammation and shrinkage of the thyroid gland in Hashimoto’s disease.
Radioactive iodine uptake
Measuring how much radioactive iodine is taken up by the thyroid helps confirm hyperthyroidism in Graves’ disease.
What is the treatment?
Treatment focuses on managing the abnormal thyroid hormone levels as well as the underlying autoimmune attack:
Thyroid hormone replacement
Taking synthetic thyroid hormone daily can restore normal hormone levels in hypothyroidism. The dose may need adjustment over time.
Antithyroid medications
Medications like methimazole and propylthiouracil prevent the overproduction of thyroid hormones in hyperthyroidism.
Radioactive iodine
Taking radioactive iodine by mouth gradually destroys overactive thyroid cells to control hyperthyroidism.
Surgery
Surgical removal of the thyroid may be recommended if other treatments fail. This is curative but requires lifelong thyroid hormone replacement.
Immune modulating medications
In some cases, medications that alter the immune response may be used to slow the autoimmune attack. Examples include steroids like prednisone or immunosuppressants.
Dietary modifications
A gluten-free or autoimmune paleo diet may help reduce antibody levels in some people by removing inflammatory foods.
Stress management
Learning to manage stress well through meditation, yoga, counseling, or other techniques may aid the immune system.
What is the outlook?
With proper treatment, most people with autoimmune thyroid disease can lead normal lives. However, there is no cure for the underlying autoimmune condition. Flare-ups can occur, requiring periodic reevaluation and adjustment of therapy.
Close monitoring of thyroid hormone levels through regular blood tests is important, especially during pregnancy. Women with autoimmune thyroiditis should be considered higher risk pregnancies.
For those with mild subclinical disease, the thyroid dysfunction may resolve on its own over time. But in most cases, lifelong treatment and monitoring are necessary.
The key is early detection and sticking with the treatment plan. While the immune system attack cannot be switched off entirely, managing the consequences can avoid long-term complications.
Conclusion
Autoimmune diseases of the thyroid are caused by the immune system mistakenly attacking thyroid proteins and cells. This leads to either overactivity or underactivity of the thyroid. While the exact triggers are unclear, genetic predisposition, infections, radiation exposure, stress and other factors may provoke the autoimmune response in susceptible individuals.
Women are at higher risk than men. Diagnosis is made by detecting elevated thyroid antibodies and abnormal thyroid hormone levels in the blood. Treatment aims to replace missing thyroid hormones or block excess production. Immune-modulating medications may also help suppress the aberrant immune attack on the thyroid.
Ongoing monitoring and adherence to treatment is crucial to restore normal thyroid function and avoid complications. While thyroid autoimmunity cannot be cured, it often can be well-managed with today’s therapies when caught early. Patients must work closely with their healthcare provider to find the optimal treatment plan. With a thorough understanding of the cause and vigilant follow-up care, most people with an autoimmune thyroid disorder can live full, healthy lives.