Hashimoto’s thyroiditis, or Hashimoto’s disease, is an autoimmune condition in which the immune system attacks the thyroid gland. This leads to an underactive thyroid, or hypothyroidism. Symptoms include fatigue, weight gain, and sensitivity to cold.

Blood tests can help diagnose the condition.

Hashimoto’s thyroiditis is the most common cause of hypothyroidism in the United States, affecting about 5% of the population.

It is most common in adult females and tends to develop between the ages of 40 and 60. It affects females at least 8 times as often as males. That said, Hashimoto’s thyroiditis can develop in anyone at any age.

Below, we provide an overview of the condition, including its symptoms, causes, and treatments.

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This issue is sometimes called Hashimoto’s disease, autoimmune thyroiditis, or chronic lymphocytic thyroiditis. The word “thyroiditis” means inflammation of the thyroid gland.

It causes the immune system to attacks the thyroid gland, a small, butterfly-shaped gland in the neck. The gland produces hormones called T3 and T4 that regulate how the body uses energy.

The immune system’s attack prevents the gland from creating enough of these hormones. A doctor may describe the issue as having an underactive thyroid or hypothyroidism.

The thyroid’s hormones affect nearly every organ in the body, and hypothyroidism can lead to problems with heart rate, brain function, and metabolism — the process of turning food into energy.

Hashimoto’s thyroiditis can sometimes also affect the body’s levels of total cholesterol, serum sodium, and serum prolactin. Indications of it may show up on a test called a complete blood count.

Many people with Hashimoto’s thyroiditis have no symptoms at first. The condition develops gradually over several years, causing progressive damage and reducing the body’s supply of thyroid hormones.

A person may develop a goiter, a noncancerous enlargement of the thyroid gland that can cause the front of the neck to appear swollen.

When the thyroid cannot produce enough hormones, it causes the pituitary gland in the brain to secrete more thyroid stimulating hormone (TSH). This causes the thyroid to grow, leading to a goiter.

When Hashimoto’s thyroiditis is responsible for hypothyroidism, the symptoms are initially mild and become more significant over time.

These symptoms include:

  • tiredness or fatigue
  • weight gain
  • sensitivity to cold
  • joint or muscle pain
  • constipation
  • heavy or irregular menstruation
  • trouble becoming pregnant
  • memory problems
  • depression
  • swelling or puffiness of the face
  • a hoarse voice

Some kinds of thyroiditis, or inflammation of the thyroid, result from infection. Hashimoto’s thyroiditis is not — it is an autoimmune disease.

The immune system’s job is to attack and remove harmful invaders such as bacteria, viruses, and toxins. Hashimoto’s thyroiditis involves the immune system mistakenly attacking thyroid gland cells as if they were harmful.

The reasons for this are unclear, but genetic factors appear to play a role. If a person has a family member with the condition, they are more likely to develop it, too.

However, even taking genetics into account, a person may not develop hypothyroidism unless they are exposed to a trigger, such as:

Also, people who consume too much or too little iodine may be more susceptible to thyroiditis.

Hashimoto’s thyroiditis can manifest in many different ways, and early symptoms can be nonspecific. As a result, a person may receive a misdiagnosis.

Conditions that can be confused with Hashimoto’s include:

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

There are also other diagnostic tests. Generally, the first step is to check the person’s serum TSH levels. High blood levels of serum TSH indicate hypothyroidism.

The pituitary gland in the brain produces TSH. Blood levels of TSH rise when the thyroid gland does not produce enough of the T4 hormone, sometimes called thyroxine.

Tests for thyroid antibodies can indicate Hashimoto’s thyroiditis. Some people with hypothyroidism do not have these antibodies.

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

Doctors treat hypothyroidism by replacing the missing thyroid hormone.

The treatment involves taking a medication called levothyroxine, a synthetic version of the hormone. This can completely control Hashimoto’s thyroiditis.

A person typically takes one levothyroxine pill each day. The necessary dosage will depend on the person’s:

  • age
  • weight
  • the severity of the condition
  • any other health issues
  • any other medications

People usually take the tablet in the morning, before they eat. It may take a few weeks for the symptoms to improve.

Older adults and people with heart disease first take a low dose, which the doctor gradually increases as needed.

Healthcare professionals will test the person’s blood periodically to see whether the dosage needs adjusting. The body is very sensitive to even small changes in thyroid hormone levels.

Some medications and supplements can interfere with levothyroxine absorption. Some foods can also have this effect, including soy products and very high-fiber foods.

Medications and supplements that may affect levothyroxine absorption include:

  • antacids that contain aluminum hydroxide
  • calcium supplements
  • iron supplements and many multivitamins that contain iron
  • some cholesterol-lowering drugs, such as cholestyramine (Questran)
  • sodium polystyrene sulfonate, which is used to treat high levels of potassium in the blood

Without treatment, Hashimoto’s thyroiditis can lead to a number of complications. These include:

  • high cholesterol
  • infertility
  • pregnancy loss
  • abnormalities present at birth

Moreover, without treatment, severe Hashimoto’s thyroiditis can result in heart failure, seizures, or a coma, and it can be fatal.

The issue may have links with Hashimoto’s encephalitis, inflammation of the brain that causes confusion, seizures, and jerking of the muscles. However, it is not clear whether there is a direct link or how the two may be related.

Research does not suggest that dietary changes can cure or prevent Hashimoto’s thyroiditis.

However, one autoimmune disease often occurs alongside another. According to some sources, thyroiditis has links with celiac disease. Other research links thyroiditis with lactose intolerance.

If a person with thyroiditis has one of these other autoimmune conditions, avoiding gluten or dairy may also help their thyroid-related symptoms.

When possible, speak about any changes to the diet or any new supplements with a physician.

Hashimoto’s thyroiditis is an autoimmune condition that leads to hypothyroidism. It is most common in adult females, but anyone can develop it.

The treatment involves taking a daily medication to replace the thyroid hormone that the body is missing.