Hashimoto's thyroiditis is an autoimmune disease in which the body's immune system attacks the thyroid gland, leading to an underactive thyroid, or hypothyroidism.

It is the most common cause of hypothyroidism in Europe and North America.

The thyroid is a small gland at the front of the neck. It produces hormones T3 and T4 that regulate how the body uses energy.

In Hashimoto's thyroiditis, the production of thyroid hormones is too low. This can lead to problems throughout the body, including heart rate, brain function, and metabolism, which is how the body turns food into energy.

A goiter may develop, a non-cancerous enlargement of the thyroid gland at the front of the neck.

Hashimoto's thyroiditis also known as Hashimoto's disease or chronic lymphocytic thyroiditis.

The American Association of Clinical Endocrinologists estimate that Hashimoto's thyroiditis affects about 14 million Americans. It is seven times more common in females than in males and is most likely to appear between the ages of 45 and 65 years.

Hashimoto's thyroiditis is less common among children, but in areas where there is too little iodine in the diet, a significant proportion of children can develop the disease.

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In Hashimoto's thyroiditis, the immune system attacks the thyroid gland.

Hashimoto's thyroiditis develops gradually over several years, causing progressive thyroid damage. The patient's levels of thyroid hormones gradually decrease.

The signs and symptoms of Hashimoto's disease overlap with other types of hypothyroidism.

They include:

  • Abnormal sensitivity to cold temperatures
  • A rise in blood cholesterol levels
  • Constipation
  • Difficulty concentrating
  • Depression
  • Dry skin
  • Enlarged neck
  • Face may appear swollen, puffed up
  • General tiredness
  • Prolonged menstruation in females, with abnormally heavy bleeding
  • Muscle pain
  • Pale skin
  • Stiffness, especially the hands and feet
  • Voice becomes hoarse
  • Weight gain that is not linked to overeating

Not everyone with hypothyroidism has the same set of symptoms.

What is a goiter?

Another manifestation of Hashimoto's is a goiter, which appears as a swelling in the front of the neck.

A lack of iodine is a common cause of goiter in places where there is not enough iodine in the diet.

In the United States Hashimoto's disease is a more frequent cause. As the immune system destroys the thyroid gland, the gland becomes unable to produce thyroid hormone. As the pituitary gland senses this, it secretes more thyroid stimulating hormone (TSH). This causes the thyroid to grow, and a goiter results.

Anyone who has a hoarse voice, constipation, a puffy and pale face, dry skin, and feels tired for no clear reason should see a doctor.

Hashimoto's disease is an inflammation of the thyroid gland. Some kinds of thyroiditis are caused by an infection, but Hashimoto's is not an infection. It is an autoimmune disease.

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Too much or too little iodine can trigger thyroid problems such as Hashimoto's.

The immune system is designed to attack and remove harmful invaders from the body, such as bacteria, viruses and toxins.

In people with an autoimmune disease, the immune system mistakes good cells for bad, and it attacks them by mistake.

Hashimoto's thyroiditis happens when the immune system mistakenly sees normal thyroid gland cells as harmful and attacks them.

Why this happens is unclear, but genetic factors appear to play a role. This does not mean that if a family member has it, an individual will also develop it and it does not affect every generation.

However, genetic factors probably mean that a person will be susceptible, but they will not develop hypothyroidism unless they are exposed to a trigger.

Triggers include:

People who consume too much or too little iodine may be more susceptible to thyroiditis. Anorexia nervosa and bulimia nervosa increase the risk, possibly because of malnutrition.

The condition has also been linked to smoking and radiation exposure.

Hashimoto's disease can manifest in different ways, and early symptoms can be nonspecific, so patients are sometimes misdiagnosed.

Conditions that may be confused with Hashimoto's include chronic fatigue syndrome, depression, fibromyalgia, an anxiety disorder, pre-menstrual syndrome (PMS), and cyclothymia.

A physician can carry out a physical examination to check for a goiter and other hallmark symptoms of hypothyroidism.

Other diagnostic tests may be carried out. Generally, the first step is to check a serum TSH.

High blood levels of Serum TSH, or thyroid-stimulating hormone (thyrotropin), indicate hypothyroidism. TSH is produced in the pituitary gland. Blood levels of TSH rise when the thyroid gland does not produce enough thyroxine.

Tests for antithyroid antibodies can also indicate Hashimoto's thyroiditis, but not everyone with the condition will have the antibodies.

Hashimoto's disease can sometimes affect the levels of total cholesterol, serum sodium, serum prolactin, and complete blood count.

If the physician diagnoses Hashimoto's thyroiditis but thyroid hormone levels are normal, and there is no goiter, the usual recommendation is for watchful waiting.

Patients who require treatment will usually need to be treated for life.

Synthetic hormone treatment

Patients with goiter or hypothyroidism will need thyroid hormone replacement therapy, for example, levothyroxine, such as Synthroid.

The patient will normally take one tablet of levothyroxine each day, but the dose must be adjusted according to age, weight, the severity of the condition, and other health issues and medications.

People with an underlying heart disease or severe hypothyroidism will start on a low dose, which is gradually increased.

Laboratory tests will be carried out from time to time, to see if a patient's dose needs adjusting, because the human body is extremely sensitive to even small alterations in thyroid hormone levels.

It may be several months before any improvement in symptoms is noticeable.

There may be some hair loss during the first few months of treatment, but this is temporary.

Some medications and supplements may interfere with levothyroxine absorption. Some foods may affect absorption as well, including soy products or very high fiber foods.

Medications and supplements that may affect levothyroxine absorption include:

  • Blood thinners, such as warfarin
  • Estrogen-containing medications, such as birth control pills
  • Sodium polystyrene sulfonate
  • Antacids that contain aluminum hydroxide
  • Calcium supplements
  • Iron supplements and many multivitamins that contain iron
  • Some cholesterol-lowering drugs, such as cholestyramine

Without treatment, Hashimoto's disease can lead to a number of complications.

These include:

  • Infertility, miscarriage, and giving birth to an infant with birth defects
  • High cholesterol

Severe cases can result in heart failure, seizures, coma, and death.

Hashimoto's thyroiditis has been associated with Hashimoto's encephalitis, an inflammation of the brain that features confusion, seizures, and jerking of muscles. However, it is not clear whether there is a direct link, or how the two may be linked.

Research does not suggest that diet can cure or prevent Hashimoto's disease.

However, one autoimmune disease will often occur alongside another. Studies suggest that some people may have hypothyroidism with low-level celiac disease. This implies that avoiding gluten may benefit some patient with hypothyroidism that stems from an autoimmune condition.

In another study of 83 patients, 75.9 percent were found to be lactose intolerant. After following a lactose-restricted diet for 8 weeks, participants experienced a significant decrease in blood levels of TSH.

Any changes to diet or use of a supplement, must, however, be discussed first with a physician.