What is Hashimoto’s thyroiditis?
Hashimoto’s thyroiditis (also called autoimmune or chronic lymphocytic thyroiditis) is the most common thyroid disease in the United States. It is an inherited condition that affects approximately 14 million Americans and is about seven times more common in women than in men. Hashimoto’s thyroiditis is characterized by the production of immune cells and autoantibodies by the body’s immune system, which can damage thyroid cells and compromise their ability to make thyroid hormone. Hypothyroidism occurs if the amount of thyroid hormone, which can be produced, is not enough for the body’s needs. The thyroid gland may
also enlarge, forming a goiter.
What are the features of Hashimoto’s thyroiditis?
Hashimoto’s thyroiditis may not cause symptoms for many years and remain undiagnosed until an enlarged thyroid gland or abnormal blood tests are discovered as part of a routine examination. When symptoms do develop, they are either related to local pressure effects in the neck caused by the goiter itself, or to the low levels of thyroid hormone. The first sign of this disease may be painless swelling in the lower front of the neck. This enlargement may eventually become easily visible. It may be associated with an uncomfortable pressure sensation in the lower neck. This pressure on surrounding structures may cause additional symptoms, including difficulty swallowing. Although many of the features associated with thyroid hormone deficiency occur commonly in patients without thyroid disease, patients with Hashimoto’s thyroiditis who develop hypothyroidism are more likely to experience the following:
• Difficulty with learning
• Dry, itchy skin
• Puffy face
• Sore muscles
• Weight gain
• Increased frequency of miscarriages
• Increased sensitivity to many medications
The thyroid enlargement and/or hypothyroidism caused by Hashimoto’s thyroiditis progresses in many patients, causing a slow worsening of symptoms. Therefore, patients with either of these findings should be recognized and adequately treated with thyroid hormone. Optimal
treatment with thyroid hormone will eliminate any symptoms due to thyroid hormone deficiency, usually prevent further thyroid enlargement, and may sometimes cause
shrinkage of an enlarged thyroid gland.
What is the cause of Hashimoto’s thyroiditis?
Hashimoto’s thyroiditis results from a malfunction in the immune system. When working properly, the immune system is designed to protect the body against invaders, such as bacteria, viruses, and other foreign substances. The immune system of someone with Hashimoto’s thyroiditis mistakenly recognizes normal thyroid cells as foreign tissue, and it produces antibodies that may destroy these cells. Although various environmental factors have been studied, none have been positively proven to be the cause of Hashimoto’s thyroiditis.
How is Hashimoto’s thyroiditis diagnosed?
A physician experienced in the diagnosis and treatment of thyroid disease can detect a goiter due to Hashimoto’s thyroiditis by performing a physical examination and can recognize hypothyroidism by identifying characteristic symptoms, finding typical physical signs, and doing appropriate laboratory tests.
Increased antithyroid antibodies provide the most specific laboratory evidence of Hashimoto’s thyroiditis, but they are not present in all cases.
TSH (THYROI D – STIMULATING HORMONE OR THYROTROPIN) TEST
Increased TSH level in the blood is the most accurate indicator of hypothyroidism. TSH is produced by another gland, the pituitary, which is located behind the nose at the base of the brain. The level of TSH rises dramatically when the thyroid gland even slightly underproduces thyroid hormone, so in patients with normal pituitary function, a normal level of TSH reliably excludes hypothyroidism.
• An estimate of free thyroxine: the active thyroid hormone in the blood. A low level of free thyroxine is consistent with thyroid hormone deficiency. However, free thyroxine values in the
“normal range” may actually represent mild thyroid hormone deficiency in a particular patient, and not drop below the “normal range” unless it becomes more severe.
• Fine-needle aspiration of the thyroid: usually not necessary for most patients with Hashimoto’s thyroiditis, but a good way to diagnose difficult cases and a necessary procedure if a thyroid nodule is also present.
How is Hashimoto’s thyroiditis treated?
For patients with thyroid enlargement (goiter) and hypothyroidism, thyroid hormone therapy is clearly needed, since proper dosage corrects any symptoms due to thyroid hormone deficiency and may decrease the goiter’s size. Treatment generally consists of taking a single daily tablet of levothyroxine. Older patients who may have underlying heart disease are usually started on a low dose and gradually increased, while younger, healthy patients can be started on full replacement doses at once. Thyroid hormone acts very slowly in the body, so it may take several months after treatment is started to notice improvement in symptoms or goiter shrinkage. Because of the generally permanent and often progressive nature of Hashimoto’s thyroiditis, it is usually necessary to treat it throughout one’s lifetime and to realize that medicine dose requirements may have to be adjusted from time to time. The body is very sensitive to even very small changes in thyroid hormone levels.
Optimal adjustment of thyroid hormone dosage should be guided by laboratory tests rather than symptoms alone. Levothyroxine tablets come in 12 different strengths, and it is essential to take them in a consistent manner every day. If the dose is not adequate, the thyroid gland may continue to enlarge and symptoms of hypothyroidism will persist. This may be associated with increased serum cholesterol levels, possibly increasing the risk for atherosclerosis and heart disease. If the dose is too strong, it can cause symptoms of hyperthyroidism, creating excessive strain on the heart and an increased risk of developing osteoporosis.
Other associated disorders
As noted above, Hashimoto’s thyroiditis is a common disorder of the immune system, which affects the thyroid gland. However, much less often, the immune system can also mistakenly
target virtually any other part of the body, causing it to malfunction, and this tendency runs in families. Although the majority of patients with Hashimoto’s thyroiditis and their genetic family members will never experience any other autoimmune condition, they do have a statistically increased risk of developing the following disorders:
• Type 1 diabetes mellitus (insulin-requiring)
• Graves’ disease (goiter and hyperthyroidism or overactive thyroid)
• Rheumatoid arthritis
• Pernicious anemia (inability to absorb vitamin B12, potentially causing anemia and neurologic problems)
• Addison’s disease (adrenal failure; the adrenal gland provides cortisol to handle stress and illness)
• Premature ovarian failure (early menopause)
• Vitiligo (patchy loss of skin pigmentation)
• Thrombocytopenic purpura (bleeding disorder due to an inadequate number of platelets in the blood)
• Lupus erythematosus (autoimmune disease that involves skin, heart, lungs, kidneys and joints)
Appropriate management of Hashimoto’s thyroiditis requires continued care by a physician who is experienced in the treatment of this disease.