Hashimoto's Thyroiditis

Hashimoto's Thyroiditis Quick Overview

  • Hashimoto's thyroiditis (Hashimoto's disease) is an autoimmune disease in which the body's immune system attacks the thyroid gland.
  • Hashimoto's thyroiditis is a common cause of hypothyroidism.
  • Symptoms of Hashimoto's thyroiditis are numerous. Common symptoms include
  • Enlargement of the thyroid gland (goiter) may be a sign of Hashimoto's thyroiditis.
  • Blood tests that measure levels of thyroid hormones, regulatory hormones, and auto-antibodies to the thyroid gland are done to establish the diagnosis of Hashimoto's thyroiditis.
  • Treatment involves the administration of thyroid hormone taken in pill form.

What is Hashimoto's thyroiditis?

Hashimoto's thyroiditis, or Hashimoto's disease, is a disorder that affects the thyroid gland. Hashimoto's thyroiditis is also known as chronic autoimmune thyroiditis and chronic lymphocytic thyroiditis. It is the most common cause of hypothyroidism in the U.S. in people over 6 years of age. It is much more common in women than in men. The peak age of onset for women is between 30 and 50 years of age; most men who are affected typically develop the condition 10-15 years later.

The name comes from the pathologist who in 1912 first described the microscopic features of the disease. Hashimoto's thyroiditis is the most common cause of hypothyroidism in iodine-sufficient areas throughout the world such as the United States. In general, there is a gradual loss of thyroid function, often accompanied by enlargement of the thyroid gland, also known as a goiter. Hashimoto's thyroiditis is most common in middle-aged women and tends to run in families.

What is the role of the thyroid gland, and what does it look like (picture)?

The thyroid gland is responsible for producing hormones that exert control over and participate in a number of metabolic functions such as temperature and heart rate regulation, and metabolism.

  • The thyroid gland produces two main hormones, thyroxine (T4) and triiodothyronine (T3), which play important roles in this regulation.
  • Control of these hormones is maintained by the pituitary gland, (which produces thyroid-stimulating hormone, TSH) and the hypothalamus (which produces thyrotropin-releasing hormone, TRH).
  • TSH regulates the production of T3 and T4 while TRH regulates the production of TSH.

If overactivity of any of these three glands occurs, an excessive amount of thyroid hormones can be produced resulting in hyperthyroidism. Similarly, if underactivity of any of these glands occurs, a deficiency of thyroid hormones can result, causing hypothyroidism.

Picture of the thyroid gland
Picture of the thyroid gland

What causes Hashimoto's thyroiditis?

The cause of Hashimoto's is thought to be a combination of a genetic predisposition along with an environmental trigger that starts the process of autoimmune destruction. What actually triggers the immune response against the thyroid gland remains unknown. Additional factors, including heredity, gender, and age, also play a role in developing this disorder.

Normally, the immune system acts to protect against viruses, bacteria, and foreign substances (antigens) that invade the body. In conditions of autoimmune disease, the immune system mistakenly attacks parts of the body itself. In the case of Hashimoto's thyroiditis, the immune system attacks the thyroid gland. The autoimmune process causes inflammation of the thyroid gland (thyroiditis) resulting in an impaired ability of the thyroid gland to produce hormones, leading to hypothyroidism. The pituitary gland responds by increasing TSH and attempting to stimulate the thyroid gland to produce more thyroid hormones. This can cause growth of the gland, or a goiter.

What are the risk factors for Hashimoto's thyroiditis?

Risk factors for Hashimoto's thyroiditis are:

  • Female gender: Women are 10-15 times more likely than men to develop Hashimoto's thyroiditis.
  • Family history: People who develop the condition often have a family history of Hashimoto's thyroiditis or other autoimmune disorders.
  • Excessive iodine intake: Excessive iodine intake is associated with a higher prevalence of Hashimoto's thyroiditis than is seen in people with mild iodine deficiency.
  • Radiation exposure: Radiation exposure has been shown to increase the likelihood of developing auto-antibodies to the thyroid gland.

22 signs and symptoms of Hashimoto's thyroiditis

The signs and symptoms of Hashimoto's thyroiditis are the same as those of hypothyroidism. The disease is slow to progress, and the onset of symptoms is gradual. It may take years for true hypothyroidism to develop.

The signs and symptoms of hypothyroidism vary widely, depending on the severity of hormone deficiency. Some of the complaints experienced by those with hypothyroidism include:

  1. Fatigue
  2. Mental fogginess and forgetfulness
  3. Feeling excessively cold
  4. Constipation
  5. Dry skin
  6. Fluid retention
  7. Non-specific aches and stiffness in muscles and joints
  8. Excessive or prolonged menstrual bleeding (menorrhagia)
  9. Depression
  10. Weight gain
  11. Puffiness in the face
  12. Infertility (difficulty getting pregnant)
  13. Thinning, brittle hair
  14. hair loss
  15. Slow heart rate
  16. Irregular menstrual periods
  17. Decreased sweating (perspiration)
  18. Thick or brittle nails
  19. Decreased reflexes
  20. Swollen hands and feet
  21. Cold skin
  22. Sleepiness

These signs and symptoms can increase in severity as the condition worsens.

What are the complications of Hashimoto's thyroiditis?

The complications of Hashimoto's thyroiditis are the same as those of an underactive thyroid gland.

Goiter: As described above, the pituitary will try to stimulate production of thyroid hormone in an underactive thyroid gland affected by Hashimoto's thyroiditis. This may cause the gland to become enlarged. Unlike a thyroid nodule, in which only a part of the gland is enlarged, in this case the entire gland enlarges, a condition known as a goiter. Goiterous glands are usually no more than a cosmetic nuisance. However, in extreme cases, growth of the gland may cause impingement on the esophagus or the trachea, impairing swallowing and breathing, respectively.

Cardiac complications: Prolonged hypothyroidism that may result from untreated Hashimoto's thyroiditis also may be associated with an increased risk of heart disease. The heart disease may be directly related to hypothyroid effects on the heart, causing changes in contraction and rhythm that may lead to subsequent heart failure. There may also be indirect influences, such as hypercholesterolemia (an increase in "bad" cholesterol is often seen with hypothyroidism).

Psychiatric complications: Depression may occur early in Hashimoto's thyroiditis and if underlying depression exists, the addition of Hashimoto's may worsen the condition. Patients may complain of mental fogginess or slowing of reaction times, and a decrease in sexual desire is often observed.

Myxedema coma: In its severest form, untreated hypothyroidism may result in a rare life-threatening condition called myxedema or myxedema coma. There is mental slowing, profound lethargy, and ultimately coma. This is a life-threatening emergency.

How does Hashimoto's thyroiditis affect and pregnancy success, risks, and complications?

Women with Hashimoto's thyroiditis who become pregnant may need an increase in their dosage of levothyroxine (see Treatment section).

Babies born to women who have uncontrolled hypothyroidism during their pregnancy may have a greater risk of birth defects than babies born to mothers with normal thyroid function. There may be a direct link with congenital defects such as cleft palate and certain brain and kidney anomalies. Data suggests that over the long term, these children may also have a higher likelihood of intellectual and developmental problems. Intervening early in pregnancy with thyroid hormone replacement may have significant benefits. Interestingly, there also are data to suggest that the presence of thyroid autoantibodies, such as those seen in Hashimoto's thyroiditis, may reduce the chance of conception.

What kind of doctor treats Hashimoto's thyroiditis?

A specialist in endocrine disorders (endocrinologist) may treat Hashimoto's thyroiditis. Primary care physicians or internal medicine specialists also may treat the condition.

How is Hashimoto's thyroiditis diagnosed?

Most people are diagnosed with Hashimoto's thyroiditis after experiencing the typical symptoms of hypothyroidism noted previously. Some patients are diagnosed without symptoms on a routine screen, and others are diagnosed after a family member is found to have the disease.

The diagnosis is made based on the results of blood tests that measure levels of thyroid hormone and thyroid-stimulating hormone (TSH). These blood tests confirm hypothyroidism, but the addition of positive autoantibody tests further points to Hashimoto's thyroiditis as the underlying cause. Antibodies can be measured in the blood. Anti-TPO (anti-thyroid peroxidase) and anti-Tg (anti-thyroglobulin) antibodies are usually seen in 85% to 90% of patients with Hashimoto's thyroiditis

What medications treat Hashimoto's thyroiditis?

If there is no evidence of hormone deficiency and only antibodies tests are positive, the use of medications is one that must be discussed in detail by the patient and doctor. Other medical conditions, patient preference, and the presence of symptoms are all taken into consideration in determining a treatment plan.

If thyroid hormone deficiency is noted on blood tests, the treatment involves daily dosing of a synthetic form of thyroid hormone. This is typically in the form of levothyroxine, which is synthetic T4 (Levothroid, Levoxyl, Synthroid).

Oral medications can restore hormone levels and reverse the symptoms of hypothyroidism, but they must be taken regularly and over the long term. Dosing is adjusted based on blood levels. Levels are usually checked every 6-12 weeks when the medication is actively being adjusted, and 6-12 months thereafter once stable.

What are the side effects of thyroid replacement therapy?

Side effects of taking too much thyroid replacement therapy are similar to those of hyperthyroidism, and may include

What about follow-up for Hashimoto's thyroiditis?

Thyroid hormone levels are usually checked every 6-12 weeks when the medication is actively being adjusted, and 6-12 months thereafter once stable. If side effects like those noted above are occurring, you should follow-up with your physician.

Can Hashimoto's thyroiditis be prevented?

There is nothing that can be done to prevent Hashimoto's thyroiditis from occurring.

What is the outlook for a person who has Hashimoto's thyroiditis?

The outlook for those with Hashimoto's thyroiditis is good. While long-term thyroid hormone replacement therapy will likely be needed, with regular blood tests and monitoring of symptoms, side effects are minimal and the long-term prognosis is good.

Reviewed on 11/17/2017

REFERENCE: Lee, S. MD. "Hashimoto Thyroiditis." Medscape. Sep 08, 2015.
<http://emedicine.medscape.com/article/120937-overview<.

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