Hypothyroidism is very common and is estimated to affect 3%-5% of the adult population. It is more common in women than in men, and the risk of developing hypothyroidism increases with advancing age.
Hypothyroidism is most commonly a result of an autoimmune condition known as Hashimoto's thyroiditis, in which the body's own immune cells attack and destroy the thyroid gland.
Introduction to Hashimoto's thyroiditis
Hashimoto's thyroiditis is the most common cause of hypothyroidism in the United States. It is named after the first doctor who described this condition, Dr. Hakaru Hashimoto, in 1912.
What causes Hashimoto's thyroiditis?
Hashimoto's thyroiditis is a condition caused by inflammation of the thyroid gland. It is an autoimmune disease, which means that the body inappropriately attacks the thyroid gland--as if it was foreign tissue. The underlying cause of the autoimmune process still is unknown. Hashimoto's thyroiditis tends to occur in families, and is associated with a clustering of other autoimmune conditions such as Type 1 diabetes, and celiac disease. Hashimoto's thyroiditis is 5-10 times more common in women than in men and most often starts in adulthood. Blood drawn from patients with Hashimoto's throiditis reveals an increased number of antibodies to the enzyme, thyroid peroxidase an enzyme (protein) found within the thyroid gland. As result of the antibodies' interaction with the enzyme, inflammation develops in the thyroid gland, the thyroid gland is destroyed, and the patient ultimately is rendered hypothyroid (too little thyroid hormone)
What are the symptoms of Hashimoto's thyroiditis?
The symptoms of Hashimoto's thyroiditis are similar to those of hypothyroidism in general, which are often subtle. They are not specific (which means they can mimic the symptoms of many other conditions) and are often attributed to aging. Patients with mild hypothyroidism may have no signs or symptoms. The symptoms generally become more obvious as the condition worsens and the majority of these complaints are related to a metabolic slowing of the body. Common symptoms are listed below:
* Fatigue
* Depression
* Modest weight gain
* Cold intolerance
* Excessive sleepiness
* Dry, coarse hair
* Constipation
* Dry skin
* Muscle cramps
* Increased cholesterol levels
* Decreased concentration
* Vague aches and pains
* Swelling of the legs
As hypothyroidism becomes more severe, there may be puffiness around the eyes, a slowing of the heart rate, a drop in body temperature, and heart failure. In its most profound form, severe hypothyroidism may lead to a life-threatening coma (myxedema coma). In a severely hypothyroid individual, a myxedema coma tends to be triggered by severe illness, surgery, stress, or traumatic injury. This condition requires hospitalization and immediate treatment with thyroid hormones given by injection.
Properly diagnosed, hypothyroidism can be easily and completely treated with thyroid hormone replacement. On the other hand, untreated hypothyroidism can lead to an enlarged heart (cardiomyopathy), worsening heart failure, and an accumulation of fluid around the lungs (pleural effusion).
There are a few patients with Hashimoto's thyroiditis who may undergo a hyperthyroid phase (too much thyroid hormone), called hashitoxicosis, before eventually becoming hypothyroid. Other symptoms and signs include:
* Swelling of the thyroid gland (due to the inflammation), leading to a feeling of tightness or fullness in the throat
* A lump in the front of the neck, (the enlarged thyroid gland) called a goiter
* Difficultly swallowing solids and/or liquids due to the enlargement of the thyroid gland with compression of the esophagus
How is Hashimoto's thyroiditis diagnosed?
In diagnosing Hashimoto's thyroiditis, a physician should assess symptoms and complaints commonly seen in hypothyroidism, examine the neck, and take a detailed history of family members. Blood tests are extremely useful in diagnosing Hashimoto's thyroiditis. The blood tests look at the thyroid function in general. (With hypothyroidism, a high thyroid stimulating hormone and low thyroid hormone would be expected.)
When hypothyroidism is present, the blood levels of thyroid hormones can be measured directly and are usually decreased. However, in early hypothyroidism, the level of thyroid hormones (T3 and T4) may be normal. Therefore, the main tool for the detection of hyperthyroidism is the measurement of the TSH, the thyroid stimulating hormone. As mentioned earlier, TSH is secreted by the pituitary gland. If a decrease of thyroid hormone occurs, the pituitary gland reacts by producing more TSH and the blood TSH level increases in an attempt to encourage thyroid hormone production. This increase in TSH can actually precede the fall in thyroid hormones by months or years (see the section on Subclinical Hypothyroidism below). Thus, the measurement of TSH should be elevated in cases of hypothyroidism. However, there is one exception. If the decrease in thyroid hormone is actually due to a defect of the pituitary or hypothalamus, then the levels of TSH are abnormally low. As noted above, this kind of thyroid disease is known as "secondary" or "tertiary" hypothyroidism. A special test, known as the TRH test, can help distinguish if the disease is caused by a defect in the pituitary or the hypothalamus. This test requires an injection of the TRH hormone and is performed by an endocrinologist (hormone specialist). The blood work mentioned above confirms the diagnosis of hypothyroidism, but does not point to an underlying cause. A combination of the patient's clinical history, antibody screening (as mentioned above), and a thyroid scan can help diagnose the precise underlying thyroid problem more clearly. If a pituitary or hypothalamic cause is suspected, an MRI of the brain and other studies may be warranted. These investigations should be made on a case by case basis.
The blood tests also usually include an analysis of antibodies (anti-thyroid peroxidase antibodies) to aid in the diagnosis.
If the gland is large- or there are symptoms of esophageal compressive, an ultrasound may be performed to see if the gland is compressing either the esophagus or the trachea (the food and breathing pipes).
What is the treatment of Hashimoto's thyroiditis?
There is no cure for Hashimoto's thyroiditis. There is no way to know how long the autoimmune process and inflammation will continue. In the vast majority of patients, hypothyroidism results from the inflammatory process.
Thyroid hormone medication can replace the hormones the thyroid made before the inflammation started. There are two major thyroid hormones made by a healthy gland (T3 and T4). Replacing one or both of these hormones can alleviate the symptoms caused by the absolute or relative lack of hormones as a consequence of Hashimoto's thyroiditis. Without medication, there is very little chance the thyroid would be able to maintain hormone levels within the normal range, and symptoms and signs of hypothyroidism would occur or worsen.
Should I be concerned if I have Hashimoto's thyroiditis and want to become pregnant?
Hashimoto's thyroiditis is not a reason to avoid pregnancy. However, some women with Hashimoto's thyroiditis do have trouble conceiving. In some patients, supplementation with selenium is used to try and decrease antibody levels. (The theory is that lower antibody levels may lead to better success in conception.) Both before and during pregnancy, the levels of thyroid hormones need to be checked to make certain they are in the optimal range for pregnancy. This is usually within the range for nonpregnant women but at the higher end of the range.
Conclusions
If you think you may have Hashimoto's thyroiditis, ask your doctor to check your thyroid and order blood tests to help make a diagnosis. If you know you have Hashimoto's thyroiditis, stay on your medication as directed by your physician and follow-up with him or her for regular thyroid blood tests, which will help you to optimize your treatment.
Hashimoto's Thyroiditis Signs, Symptoms, Causes, Diagnosis, and Treatment by MedicineNet.com
