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The Most Common Thyroid Disease: A Deeper Look

by Christopher M. Cirino, DO MPH and Julian Dollente, RN.

The endocrine systems consist of multiple tissues, organs, and glands distributed throughout the body. It interacts with the immune system. While the body employs the immune system to protect from foreign invaders, it sometimes attacks the body’s cells, such as your thyroid gland.

Hashimoto’s is the most common thyroid disorder in the United States, affecting approximately 1-2% of the American population.  Hashimoto’s Thyroiditis is a type of autoimmune disorder and is named after Hakaru Hashimoto, a Japanese physician who first described the thyroid changes of the disease in 1912.

This article reviews Hashimoto’s Thyroiditis, addressing the risk factors, signs and symptoms, and the best treatment and management options. aving the proper knowledge is what you need to avoid illnesses. 

To better understand Hashimoto’s Thyroiditis, we should first discuss the thyroid and its effects on our body. The thyroid is one of the eight major glands in the endocrine system that produces hormones crucial for the human body’s metabolism, growth, and development. 

Located at the base of your neck is the thyroid gland, which is a butterfly-shaped organ that is responsible for releasing two main hormones:

  • Triiodothyronine (T3)
  • Thyroxine (T4) 

T3 and T4 are hormones that regulate numerous vital body functions, and any changes in the level of these two hormones can have adverse effects on the following body functions:

  • Breathing
  • Heart rate
  • Central and peripheral nervous system
  • Bodyweight
  • Muscle strength 
  • Menstrual cycles
  • Body temperature
  • Cholesterol metabolism
thyroid tissue showing scarring and infiltration of lymphocytes, characteristic for HT
Sample showing fibrotic changes throughout thyroid tissue c/w Hashimoto’s. Source: Wikimedia Commons.

Hashimoto’s Thyroiditis Causes

Like all autoimmune diseases, Hashimoto’s Thyroiditis is caused by a malfunction in the immune system wherein immune cells, known as lymphocytes, attack healthy tissue and lead to inflammation and scarring. They reduce the thyroid’s ability to produce hormones, leading to hypothyroidism. In extreme cases, the invading immune cells can cause inflammation and enlargement of the thyroid to the point that it makes a visible mass in the neck (a goiter).

Hashimoto’s Thyroiditis Risk Factors

The exact cause of Hashimoto’s Thyroiditis remains unclear. However, there are several factors that increase the likelihood of Hashimoto’s disease, including:

  • Sex: Women
  • Age: 30 – 50 years old
  • Family history: Direct relatives with thyroid problems or autoimmune diseases
  • Preexisting autoimmune condition: Addison’s disease, rheumatoid arthritis, lupus, type 1 diabetes, or certain liver conditions.
  • Radiation exposure: Organochlorine pesticides, BCPs, BPA, etc. 

How the Environment Affects Hashimoto’s Thyroiditis

Research has shown certain environmental exposures can trigger Hashimoto’s disease. Examples of these include:

Changes in the environment

People have been fighting against microorganisms that have tried to invade our bodies as part of our evolution. The human immune system has coevolved with our need to defend our bodies from outside harm through the years. In the past century, however, our environment has turned increasingly sanitary. 

While this may be a positive development for our overall health, it also contributed to more allergic and autoimmune diseases. It left our immune system with fewer pathogens to activate it. Scientists refer to this phenomenon as the hygiene hypothesis.

Excess in dietary iodine

Iodine can help reduce goiter in people with Hashimoto’s. However, too much iodine can aggravate Hashimoto’s disease in people with a genetic predisposition. Additionally, iodine controls the production of reactive oxygen species (ROS) — which in excess can be toxic for the thyroid gland. 

Inadequate dietary selenium intake

Evidence links selenium supplementation to reducing antibodies that target and destroy the thyroid gland. Furthermore, one large study is underway that may clarify this hypothesis. 

Exposure to Chemicals

Living in the vicinity of a petrochemical complex

People living near petrochemical complexes such as oil refineries have a higher risk of developing Hashimoto’s and antibodies that attack the thyroid. 

Synthetic Pesticides

Exposure to insecticides and fungicides puts people at a higher risk of developing hypothyroidism. People exposed to pesticides — including an unborn child — causes the development of goiter, an increase in thyroid peroxidase (TPO) antibodies, and manifestations of signs of other autoimmune diseases, including diabetes. 

Polychlorinated Biphenyls (PCBs)

PCBs are manufactured chemicals. You can acquire them through eating PCB-containing foods. Another form of entry is through your skin. For example, frequently swimming in areas with high PCBs increases the chances of the PCBs entering your body through the skin. 

PCBs can trick the body into mistaking them for hormones causing hormonal imbalance. They also reduce the concentration of thyroid hormones in the bloodstream. Many countries have restricted the use of PCBs due to environmental concerns.

Bisphenol-A (BPA)

Plastic or ceramic compounds such as polycarbonate plastics and epoxy resins coat food cans; dental sealants contain BPA. It is an endocrine disruptor known for its estrogenic activity; it may act directly on the thyroid gland disrupting thyroid hormone function.

Increased BPA exposure also elevates the level of TPO antibodies. Research suggests that BPA exposure in pregnant women causes increased inflammation in their offspring and predisposes an individual to thyroid problems even before birth.

Hashimoto’s Thyroiditis: Symptoms

Hashimoto’s Thyroiditis can be asymptomatic, which means people who have them can go years without experiencing problems. The main symptoms of Hashimoto’s fall in two categories: goiter and hypothyroidism.


The term “goiter” is used for any enlargement of the thyroid gland, and not necessarily that the thyroid isn’t functioning. It is most commonly associated with iodine deficiency worldwide. Goiter shows as swelling in the neck and, in the US, goiter is most associated with HT.

In Hashimoto’s, the immune cells attack the thyroid gland and lead to inflammation and enlargement of the tissue. The lump may be painless at first, but it can grow bigger if left untreated. An advanced goiter can put increased pressure on your lower neck, making it difficult to swallow or even breathe. 

Symptoms of Hypothyroidism

Hashimoto’s Thyroiditis is the most common cause of hypothyroidism. A depleted thyroid hormone level can negatively impact certain functions of your body. Signs and symptoms of hypothyroidism may include:

  • Fatigue
  • Weight gain
  • Increased sensitivity to cold
  • Difficulty concentrating
  • Dry skin, nails, and hair
  • Constipation
  • Drowsiness
  • Muscle soreness
  • Increase menstrual flow
  • Cholesterol metabolism (elevated LDL)
  • Elevated blood pressure
  • Sleep Apnea

Hashimoto’s Thyroiditis: Diagnosis, Treatment, and Management

If you are experiencing any signs of fatigue or weight gain, consult with your doctor for thyroid screening. A simple blood test can confirm hypothyroidism. The screening blood tests are Thyroid stimulating hormone (TSH) and Free-T4 (FT4) – a test of unbound T4. A high TSH (>10) and low T4 confirms hypothyroidism from thyroid gland failure. The majority of patients with Hashimoto’s thyroid disease also have elevated auto-antibodies Thyroid peroxidase Ab (TPOAb) and/or Thyroglobulin Ab (TGAb).

The only treatment necessary for Hashimoto’s Thyroiditis is thyroid hormone replacement therapy when significant dysfunction exists. The hormone replacement satisfies the body’s needs of a normally functioning thyroid. The main medication is a synthetic supplement known as levothyroxine. Less commonly, Armour Thyroid is a natural preparation, but it isn’t FDA approved to treat hypothyroidism.

T4 is the primary circulating thyroid hormone, making up about 95% between T4 and T3. Taking levothyroxine helps turn T4 into T3 hormone. The replacement therapy compensates for the thyroid’s deficient hormones. A patient needs to stay on the therapy and monitor its effectiveness.

Doctors check a blood test known as Thyroid Stimulating Hormone (TSH), which the pituitary gland secretes to signal the thyroid. When the level is insufficient, the TSH will be high. Doctors titrate the dose of levothyroxine to achieve a normal TSH, about 0.5 to 5.0 mIU/L range. They can also check a Free T4, a more accurate representation of thyroid hormone.

Role of Diet in the Management of Hashimoto’s Thyroditis

While there are many dietary claims of benefiting Hashimoto’s thyroiditis, there are no clear guidelines for an autoimmune diet. Likely the best diet for HT is one that is low in added sugar and ultra-processed foods. These diets have been shown to reduce blood inflammatory markers and may be beneficial for many chronic diseases.

Online lifestyle programs have been studied. These suggest that an “Autoimmune Protocol Diet” as part of a multidisciplinary program were effective in the participants’ health-related quality of life (HRQL), symptom burden, and markers of inflammation (Abbott, 2019).

The effect of a gluten was tested recently as a pilot study. After six months, the 16 women fed a gluten-free diet showed lower levels of TPOAb and TGAb titers. Lower titers suggest decreased immune activity, but it is unclear in the study if there were any clinical changes (Krysiak, 2018). Further studies are needed.

An elimination/reducing diet in women with obesity and HT showed that certain diets were favorable, reducing TSH levels and increasing FT4 levels compared to a balanced reducing diet in one study. Diets that are high in processed foods are known to increase inflammatory markers and could also play a role in fueling autoimmune processes.

Likely the best diet for HT is one that is low in added sugar and ultra-processed foods.

Photo by Noelle Otto on Pexels.com

Summing it up

Hashimoto’s Thyroiditis is an autoimmune disorder that leads to loss of function of the thyroid. You may experience weight gain, fatigue, constipation, joint and muscle pain, and difficulty getting pregnant. 

There is no cure for Hashimoto’s. At the point that there is loss of function, a person will require thyroid hormone replacement with a maintenance medicine containing thyroid hormone (T4),

A healthy lifestyle along with eating right, getting enough sleep, exercising, and regulating stress levels can be a helpful immune. A low sugar, low processed food diet, and gluten free diet might benefit the trajectory of the disease.  


Abbott RD, Sadowski A, Alt AG. Efficacy of the Autoimmune Protocol Diet as Part of a Multi-disciplinary, Supported Lifestyle Intervention for Hashimoto’s Thyroiditis. Cureus. 2019 Apr 27;11(4):e4556. doi: 10.7759/cureus.4556. PMID: 31275780; PMCID: PMC6592837.

Krysiak R, Szkróbka W, Okopień B. The Effect of Gluten-Free Diet on Thyroid Autoimmunity in Drug-Naïve Women with Hashimoto’s Thyroiditis: A Pilot Study. Exp Clin Endocrinol Diabetes. 2019 Jul;127(7):417-422. doi: 10.1055/a-0653-7108. Epub 2018 Jul 30. PMID: 30060266.

Other references are included in the links.

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