2.1 - THYROID SUPPRESSION TEST WITH L-THYROXINE [TST4] AND [Tc-99m]PERTECHNETATE.

Ramos CD, Zantut-Wittmann DE, Tambascia MA, Assumpção LVM, Etchebehere ECSC, Camargo EE. Division of Nuclear Medicine, Department of Radiology and Department of Internal Medicine, Campinas State University (UNICAMP), Campinas, Brazil.

TST4 has been demonstrated as being as effective as the classical T3 and [I-131]iodide thyroid suppression test with the advantages of less side effects, ease of administration, low dosimetry and shorter duration. To evaluate the effectiveness of TST4 in demonstrating autonomous thyroid tissue, 20 patients (pts) with autonomous thyroid disease (18 females and 2 males; 27 to 83 years, mean 53.6 years) were studied. The pts were divided into 4 groups: 7 with non-toxic autonomous nodule (NTAN), 3 toxic autonomous nodule (TAN), 7 with euthyroid Graves´ disease but with laboratory proven active disease and 3 with diffuse toxic non-autoimune goiter (DTNAIG). Ultra-sensitive TSH, free-T4 and anti-thyroperoxidase and anti-thyroglobulin antibodies levels were obtained in all pts. Four pts were on metimazol. Twenty minutes after an intravenous injection of 370 MBq (10 mCi) of [Tc-99m] pertechnetate thyroid uptake and scintigraphy were performed. Thyroid uptake and images were repeated after 10 days of oral L-thyroxine (L-T4) (2 mg/kg, single dose). Baseline thyroid uptake ranged from 0.7 to 12% (mean 3.0%). After suppression thyroid uptake ranged from 0.5 to 10% (mean 2.8%), with an average reduction of 6.7%. Thyroid uptake decreased in 10 pts (maximum reduction = 39%, mean 21%), uptake was unchanged in 2 pts and increased in the remaining 8 pts.. In 5 of the NTAN pts (four with a solitary nodule and 1 multinodular) the extra-nodular parenchyma had reduced uptake, but was visible; however, after suppression the uptake of the extra-nodular parenchyma declined even further, while the nodular uptake remained unchanged. There was no significant difference in the images acquired after suppression in pts with TAN, Graves´ disease and DTNAIG. TST4 is an effective method to demonstrate autonomous thyroid tissue.

Making use of Lakshmanan et al definite prohibitions, and Maxon et al. lists of allowed foods, the author worked out a richer, comprehensive and autoexplicit diet. The mechanisms of uptake increase, the efficiency in favoring iodine depletion and scanning, the potential benefit for I-131 ablation, but unproved for I-131 treatment of differentiated thyroid cancer, are exposed. The usefulness of urinary iodine assay to avoid contamination, to advise a LID need, to appraise adherence to, and efficiency of LID, is stressed. It is to regret non-adoption of LID in face of increased iodine intake, as it is to condemn increase in I-131 dose, in this context, since LID is quickly efficient and harmless. In countries like Brazil, an algorithm is suggested: 1. To estimate foods iodine content, or 2. To obviate contamination, by urinary iodine assay, or 3. To prescribe a LID. The axiom: "Maybe sometimes LIDs are unhelpful, contamination is allways harmfull" is proposed.

2.3 - FALSE-POSITIVE I-131 WHOLE-BODY SCANNING.

Henry Wolff, Dinis José Breda, Neivo da Silva

There are an increasing number of conditions that lead to false-positive I-131 whole-body scans, with serious consequences in differentiated thyroid cancer management. They are classified in five main groups, according to mechanism: elimination of iodine in body fluids, inflammation and infection, transudates and cysts, nonthyroid neoplasms, and miscellaneous, discussed by the authors, who present their own experience, including tooth inflammation (5 patients), inflammation on the nose (hot nose), and parotid gland duct ectasia. The last is the first one reported on the medical literature. The demonstration of the false-positive nature of the findings avoided unnecessary I-131 treatment. Appropriate steps to disclose spurious cases are exposed.

2.4 - PARAGANGLIOMA FUNCIONANTE (PF) DO PESCOÇO-REVISÃO BIBLIOGRÁFICA

Villela, JR; Abuhid, I; Pimenta, T; Bambirra, E; Pardini, V. - Laboratório de Patologia Clínica Hermes Pardini - MG

Apresentamos um caso de PF no pescoço em uma criança de 11 anos de idade cujo diagnóstico foi estabelecido pela cintilografia com I131-MIBG. Apresentamos este caso por tratar-se de patologia rara (menos de 1% dos casos são funcionantes) e para demonstrar o papel decisivo da cintilografia (CTG) com I131-MIBG no diagnóstico e conduta terapêutica. PF são tumores raros, produtores de catecolaminas que se originam da crista neural. Este paciente apresentava-se com quadro de hipertensão arterial grave, massa na região cervical direita e aumento de catecolaminas e metabólitos urinários. A CTG com I-131-MIBG mostrou a presença de massa hipercaptante em região cervical direita, confirmada pela ressonância nuclear magnética (RNM). A RNM mostrou também uma lesão contra-lateral que entretanto não apresentou captação pelo I131-MIBG. Foi realizada exérese da lesão cervical direita evoluindo com normalização da pressão arterial, catecolaminas e metabólitos urinários. O paciente será acompanhado com exames clínicos e laboratoriais periódicos especialmente pela presença da lesão contra-lateral não ressecada. A CTG com I-131 deve ser utilizada como primeiro método diagnóstico na pesquisa dos tumores (TU) neuroendócrinos por localizar o TU, especialmente extra adrenais, detectar múltiplos metastáticos, TU<2,0 cm, fornecer dados funcionais além de anatômicos e por ser o mais específico dentre os métodos diagnósticos utilizados

Almeida Filho PJ, Lemos MR, Freita AC, Almeida CA, Borges Neto, S.