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Laboratory Testing in Thyroid Cancer for Diagnosis and Follow-Up—the Old and the New


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April 2008

Thyroid cancer develops in your thyroid, a butterfly-shaped gland located at the base of your neck, just below your Adam's apple. Patients require long-term follow-up surveillance for tumor recurrence. Thyroglobulin (Tg) is the key tumor marker to detect recurrence of follicular cell-derived tumors. Serum concentrations of Tg are highly specific for the presence of thyroid tissue in the body, but they are not specific for malignancy. The newest-generation Tg assays, which have been available for the past 6 years and are used routinely at Mayo Clinic, have 4- to 10-fold better detection sensitivity than the older assays, thus in many cases obviating the need for stimulated Tg measurements. One benefit from these new observation methods is most patients with Tg levels <0.1 ng/mL might not require fine-needle aspiration (FNA) biopsy of enlarged neck nodes. However, those patients with detectable serum Tg or Tg antibody should undergo FNA biopsy of enlarged or questionable neck nodes. Normal lymph nodes do not contain Tg and, therefore, any detectable Tg in a node is highly suspicious for metastatic thyroid cancer. The FNA biopsy Tg measurement with a cutoff of 1.0 ng/mL has 100% sensitivity and 96.2% specificity.

Graves’ disease in children

Graves' disease is a type of autoimmune disease that causes overactivity of the thyroid gland, causing hyperthyroidism. Girls are 4 to 5 times more likely to be affected than boys. Subtle symptoms like anxiety, hyperactivity, declining school performance, and nocturia in children are observed before hyperthyroidism is diagnosed. In Graves' disease, circulating levels of thyroid hormones—thyroxine (T4) and triiodothyronine (T3)—are increased, while thyroid-stimulating hormone (TSH) is suppressed. Treatment options for children with Graves’ disease include antithyroid medications, thyroidectomy, or radioactive iodine. No one treatment available is appropriate for every patient. A thorough discussion with the child and parents regarding the advantages and disadvantages of each treatment modality is essential to provide appropriate individualized treatment.

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