32
Hashimoto Thyroiditis
David L. Steward
History
A 42-year-old woman describes progressive fatigue, lethargy, and weight gain. She has no known medical problems. She takes no prescription medications but does take a multivitamin daily. She reports a family history of hypothyroidism but denies a family history of thyroid cancer. She denies a history of radiation exposure.
Physical examination reveals a firm thyroid gland bilaterally but is otherwise normal.
Differential Diagnosis—Key Points
This patient has symptoms of hypothyroidism, although these symptoms are not specific, and biochemical thyroid function testing is required to confirm the diagnosis. The most common cause of hypothyroidism in the United States is chronic lymphocytic thyroiditis, or Hashimoto thyroiditis, although antithyroid antibodies are rarely necessary for patient management. In older patients, hypothyroidism might not be the result of thyroiditis but rather a consequence of aging. Outside the United States, in iodine-deficient areas, hypothyroidism may be due to endemic iodine deficiency.
Test Interpretation
Thyroid-stimulating hormone (TSH) and free thyroxine (T4) are indicated to confirm the suspected diagnosis of hypothyroidism, which is associated with a high TSH and low or normal free T4. Free tri-iodothyronine (T3) testing is generally not needed to confirm hypothyroidism, in contrast to hyperthyroidism. Antithyroid peroxidase (TPO) and thyroglobulin antibodies are rarely necessary but can confirm the cause as Hashimoto thyroiditis.
