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Hashimoto’s Disease: A Form of Hypothyroidism

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Hashimoto’s disease, or Hashimoto’s thyroiditis, is a thyroid autoimmune disease and a condition where the immune system attacks and damages the cells of the thyroid gland. It is the most common cause of hypothyroidism and affects more women than men, appearing between the ages 40 and 60. It was first reported by a Japanese physician Hakaru Hashimoto in 1912. Although it is estimated that about 1-2% of people suffer from Hashimoto’s disease in the United States (U.S.), there has been a lack of data for the actual prevalence in Asian countries. A separate study based on active military personnel in the US has found that Hashimoto’s disease was most commonly found in whites, and least commonly found in Asians.

What is Hashimoto’s disease?

Hashimoto’s disease is a type of hypothyroidism where the thyroid does not create and release enough thyroid hormones in the bloodstream. The thyroid is a small endocrine gland located in the front of the neck that produces thyroid hormones, which regulate the body’s metabolism and body temperature to enable proper organ function. Decreased levels of thyroid hormones causes the slowing of metabolism and can make one feel tired and lethargic

The mechanism behind Hashimoto’s disease involves white blood cells (CD4 positive T cells) becoming self-reactive where they recruit antibody-producing white blood cells (B cells) and special killer CD8 positive T cells generated in the thymus to destroy thyroid hormone-producing cells of the thymus. 

Symptoms of Hashimoto’s disease

Hypothyroidism in the early stages presents with mild non-specific symptoms that escape diagnosis until routine blood screening tests are conducted. Some early symptoms may include:

  • Dry skin
  • Weight gain
  • Constipation 
  • Fatigue 

These symptoms can progress to become more advanced symptoms within months, but can take up to a few years to evolve into serious disease states in some patients. These advanced symptoms may include:

  • Increased fatigue and loss of energy
  • Cold intolerance 
  • Hoarse voice 
  • Memory loss
  • Depression and psychiatric disturbances
  • Hair loss
  • Menstrual irregularities
  • Pressure in the neck 
  • Muscle cramps 

Some patients may also develop an enlarged thyroid gland (goitre) where there is swelling in the neck, causing discomfort and difficulty in swallowing. 

Diagnosis of Hashimoto’s disease

Hashimoto’s disease is confirmed through laboratory testing conducted in patients who are suspected to have the condition upon clinical presentation of symptoms. A high TSH level alongside low free T4s, as well as the presence of positive autoantibodies, is indicative of Hashimoto’s disease. 

High TSH levels

The serum thyroid-stimulating hormone (TSH) test is a sensitive blood test that is indicative of thyroid function. A high level of TSH signifies primary hypothyroidism which can be mainly attributed to Hashimoto’s disease when corroborated with the following markers. 

Low free T4 levels 

Thyroxine, also known as T4, is the main form of thyroid hormone that circulates in the blood. Low levels of free T4 indicate hypothyroidism. 

Positive autoantibodies 

A blood test can confirm the presence of specific antibodies produced in patients with Hashimoto’s disease. Autoantibody detection can be conducted using serum from blood samples via a sensitive chemiluminescent immunoassay (CLIA) technique. 

Elevated Anti-TPO antibodies 

A blood test can confirm the presence of anti-thyroid peroxidase (anti-TPO) antibodies. TPO is an enzyme of the thyroid gland that is responsible for the production of thyroid hormones. The presence of anti-TPO antibodies suggests thyroid dysfunction and is commonly found in patients with Graves’ disease and Hashimoto’s disease.  

In patients where there is a strong family history of thyroid disease, TPO levels may be higher than the average healthy population, but symptoms of hypothyroidism may not be present.

Anti-Tg antibodies 

Anti-Thyroglobulin (anti-Tg) antibodies are autoantibodies produced by patients with Hashimoto’s disease against thyroglobulin, a protein made by the follicular cells of the thyroid gland to produce triiodothyronine (T3) and T4, which are responsible for the production of thyroid hormones. The presence of these autoantibodies indicates that the thyroid gland is being attacked. 

Complications of Hashimoto’s disease

Hashimoto’s thyroiditis is more common in patients with other autoimmune diseases such as Type 1 diabetes, coeliac disease, individuals with Down syndrome and multiple autoimmune diseases. 

If hypothyroidism from Hashimoto’s disease is left untreated, the disease can cause:

Monitoring of disease is essential in patients that present with hypothyroidism complications. Therefore, the following tests are very useful in identifying and evaluating other co-morbidities:

  • Complete blood count: Test for presence of anaemia that may be present in up to 40% of patients 
  • Total lipid profile: Monitors cholesterol, LDL and triglyceride levels 
  • Creatine kinase levels: Essential for monitoring in patients with severe hypothyroidism
  • Metabolic panel: Monitors kidney health and function

Myxoedema coma 

Myxoedema is a rare and severely advanced hypothyroidism that has been left untreated. It can cause progressive lethargy, low heart rate (bradycardia), lowered body temperature (hypothermia) and multiple organ dysfunction that can lead to death. 

Treatment of Hashimoto’s disease

The treatment choice for Hashimoto’s disease, as with most hypothyroidism cases, is levothyroxine, a type of synthetic thyroxine that is taken for life. Levothyroxine is very effective at improving the symptoms of hypothyroidism but requires careful tailoring of drug dosage in the beginning of administration until TSH concentration levels are stable. 

Women of childbearing age should receive an increased dose of levothyroxine when pregnant

In patients with elevated TPO antibodies but have normal thyroid function tests, medication is not needed.

Levothyroxine and dietary interactions

Levothyroxine interacts with many types of food that are rich in calcium and iron. This interaction specifically refers to how levothyroxine binds to these minerals, leading to a decrease in the absorption of the medication. Although our Asian diet does not typically contain a high amount of dairy products, we should still note that absorption of this medication can be greatly reduced when taken with milk, which is commonly added to our morning coffee or tea. Dark leafy vegetables rich in iron like spinach and broccoli, alongside red meat and organ meats like liver which is popular in the Asian diet may also exert the same effect.

To ensure the medication is absorbed fully and the dose of the medication can be titrated to a stable level, levothyroxine should be administered on an empty stomach or separated from these interacting agents by 4 hours.

Conclusion

Hashimoto’s disease is a pathological thyroid hormone deficiency. Despite being a treatable disease that does not affect life expectancy, it is essential that medical attention is sought promptly when symptoms of disease start appearing.

Last medically reviewed, 22 July 2022. 

 

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