RESUMO
Papillary and follicular thyroid cancers, together termed differentiated thyroid cancers (DTC), comprise the majority of thyroid carcinomas and have an optimal prognosis. Most DTCs appear as asymptomatic thyroid nodules. Fine-needle aspiration (FNA) cytology is the first diagnostic test for a thyroid nodule in a euthyroid patient. Surgery is the primary treatment for thyroid cancers. Most clinicians recommend near-total or total thyroidectomy, and then 131I ablation therapy, since its consequences are minimal and follow-up is facilitated. A total body scan (TBS) is performed 4 to 7 days after 131I treatment. At a later stage, all patients should be treated with L-tiroxine so as to suppress TSH, and must undergo a periodic evaluation of TSH and thyroglobulin (Tg), the most sensitive and specific marker of DTC. After 6-12 months, TBS with 131I is performed, a technique complementary to serum Tg evaluation. For this technique, it is also necessary to have a high serum TSH concentration, obtained by withdrawing thyroxine therapy for 4 to 6 weeks. This standard method induces hypothyroidism. An alternative method to the withdrawal of thyroid hormones in the follow-up of DTC patients is to administer recombinant human TSH (rh-TSH). After the dose of rhTSH, 131I is administered, and then TBS can be performed 48-72 hours later. Currently, several authors have explored the possibility that rh-TSH-stimulated Tg levels may represent the only necessary test to differentiate patients with persistent disease from disease-free patients, without performing a diagnostic TBS.
