Description

• Autoimmune lymphocytic infiltration of the thyroid gland closely associated with the presence of antithyroid autoantibodies and often resulting in chronic hypothyroidism
• Sometimes associated with a euthyroid state or transient hyperthyroidism
• Most common form of chronic thyroiditis

ICD-9 code

• 245.2 chronic lymphocytic thyroiditis

Who is most affected

• Females
• Peak age of onset: 30-50 years
• Inherited as a dominant trait—up to 50% of first-degree relatives may have a history of Hashimoto thyroiditis or the presence of thyroid autoantibodies in their serum.

Incidence/prevalence

• Overall U.S. prevalence approximately 4.6%
• Estimated prevalence by gender 5.8% for females and 3.4% for males (CDC data)

Risk factors

• Postpartum state (i.e., postpartum thyroiditis)
• Specific alleles (HLA-DR3, HLA-DR4, HLA-DR5) in Caucasian populations
• Elevated iodine intake (at least 0.5 mg/day)
• Selenium deficiency
• Amiodarone
• Exposure to ionizing radiation
• Turner syndrome
• Cigarette smoking
• Vitamin D receptor (VDR) gene variants
• Breast cancer

Complications

• Hypothyroidism
• Hyperthyroidism
• Hashimoto encephalopathy (responsive to steroids)
• Thyroid lymphoma

Associated conditions

• Diabetes mellitus type 1 
• Autoimmune adrenal insufficiency (Addison disease)
• Autoimmune polyglandular syndrome type II (adrenal insufficiency, thyroid disease, and/or type 1 diabetes mellitus)
• Atrophic body gastritis/pernicious anemia
• Other autoimmune disorders, such as vitiligo and premature ovarian failure
• POEMS syndrome [polyneuropathy, organomegaly, endocrinopathy, M protein, skin changes]
• Primary biliary cirrhosis
• Psychiatric disorders, such as depression, generalized anxiety disorder, or social phobia

History

• Symptoms of hypothyroidism (lethargy, constipation, cold intolerance)
• Symptoms of hyperthyroidism (nervousness/anxiety, muscle weakness, diarrhea, heat intolerance, etc.) — less common
• Asymptomatic goiter

Physical

• Findings of hypothyroidism (weight gain, facial puffiness, dry skin, hair loss, hoarseness, etc.)
• Findings of hyperthyroidism (weight loss, tachycardia, fatigue, etc.)
• Diffuse, symmetrically enlarged, painless goiter approximately two to three times normal size is present in 90% of patients, while 10% have thyroid atrophy.

Making the diagnosis

• Serology to confirm presence or absence of thyroid disease, including thyroid-stimulating hormone and free thyroxine
• Testing for the presence of antithyroid autoantibodies, including antithyroid peroxidase antibodies (90%-95% sensitive for Hashimoto thyroiditis) and possibly antithyroglobulin antibodies (much less sensitive and may not be test of choice)
• Ultrasound may reveal a hypoechogenic thyroid.
• Consider erythrocyte sedimentation rate, antinuclear antibody, and serum protein (hypergammaglobulinemia/monoclonal gammopathy) determinations.
• Rule out other causes of painless thyroiditis (subacute lymphocytic, drug-induced, and fibrous thyroiditis [Riedel thyroiditis]) and diffuse toxic goiter (Graves disease).

Prognosis

• Presence of serum antithyroid antibodies associated with increased risk for future development of hypothyroidism
• Patients with subclinical Hashimoto thyroiditis may progress to overt hypothyroidism at a rate of <5% per year.

Treatment

• Treatment for acute/chronic hypothyroidism (thyroxine supplementation) or hyperthyroidism as needed (Treatment with thyroxine for more than one year in patients with hypothyroidism may be associated with a return to euthyroid state after thyroxine discontinuation in up to 25% of patients.)
• Iodine restriction (may also result in a return to euthyroid state)
• Thyroid hormone therapy in patients with euthyroid Hashimoto disease associated with improvements in thyroid function tests, decreased levels of serum antithyroid autoantibodies, and a reduction in goiter size
• Selenium supplementation is associated with a reduction in thyroid peroxidase antibody levels and may improve patient’s subjective sense of well-being.

Screening and prevention in pregnancy

• Selenomethionine treatment during and after pregnancy may prevent postpartum thyroid dysfunction.
• Women with a history of autoimmune thyroiditis should be monitored during and after pregnancy for disease progression.

For complete references, see www.dynamicmedical.com.

Dr. Brier is an editor for DynaMed, a database of comprehensive updated summaries covering nearly 3,000 clinical topics. Dr. Brown is a neurologist and deputy editor for DynaMed.