A 35-year-old woman is seen in the Endocrine Clinic for evaluation of thyroid disease. The patient complains of weight loss, irritability, and restlessness. Physical examination reveals enlargement of the thyroid gland, weakness in maintaining the leg in an extended position, warm moist skin, and tachycardia. Family history indicates that the patient's mother had hypothyroidism after the birth of the patient's brother and an aunt had Hashimoto's disease.
1. Based on the history and physical examination, what would be a reasonable initial diagnosis?
2. From a blood sample, what hormone concentrations should the laboratory measure, and what would be the likely results?
3. What antibody titers should the laboratory determine? Which antibody titer is the most useful in the diagnosis of Hashimoto's disease?
4. Which antibody titer would be most useful in the diagnosis of Graves' disease?
5. The antibody titers indicate that the patient has Graves' disease. What treatment would be appropriate for this patient?
1. The physical findings, including the presence of goiter, suggest that the patient may be hyperthyroid. However, goiter can also occur in hypothyroidism. Since autoimmune thyroid disease runs in families, the family history suggests that the thyroiditis might be due to an autoimmune response.
2. The laboratory should determine the blood levels of thyroid hormones (T4 and T3) and TSH. Thyroid hormones should be increased. TSH may be increased if it is early in the progression of Hashimoto's disease or decreased if the patient has Graves' disease.
3. The laboratory should measure antibodies to TSH receptor, thyroid peroxidase, and thyroglobulin. Antibodies to thyroid peroxidase are elevated to the greatest extent in Hashimoto's disease.
4. Antibodies to TSH receptor, thyroid peroxidase, and thyroglobulin can all be elevated in Graves' disease. However, the presence of TSH receptor antibodies is diagnostic.
5. A thionamide compound should first be used to inhibit thyroid hormone synthesis. This treatment will relieve the symptoms of hyperthyroidism and may result in a reduction in immune response. The drug may be withdrawn after several months of treatment to determine whether the disease is in remission. If thyroid hormone levels increase with cessation of the drug, ablation of the thyroid gland with 131I (or less commonly with surgery) would be indicated.
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