Avaliação do impacto da dieta pobre em iodo na concentração do iodo urinário e na capacitação do radioiodo pela tireóide em pacientes com Bócio Multinodular

Abstract

Resumo: Nas ultimas decadas a dieta pobre em iodo vem sendo usada antes do tratamento com 131I em pacientes com doencas da tireoide com o intuito de aumentar a captacao do iodo radioativo pela tireoide. Porem, ate o momento nenhum estudo comprovou convincentemente esse fato. Esse estudo tem como objetivos analisar as diferencas nas taxas de captacao de iodo radioativo nos pacientes portadores de bocio multinodular (BMN), utilizando ou nao dieta pobre em iodo (DPI), analisar a taxa de excrecao urinaria de iodo apos a DPI e o volume da tireoide apos I131. Foram avaliados 30 pacientes portadores BMN e destes 9 foram excluidos. Os pacientes foram divididos em 2 grupos: grupo 1 (n=11), submetidos a DPI (30 a 50ƒÝg por dia); e grupo 2 (n=10) submetidos a dieta regular (DR). Antes da dieta foram verificados: T3, T4, TSH, cintilografia, analise volumetrica com ecografia e medida do iodo urinario. 15 dias apos a dieta foram analisados novamente com cintilografia e dosagem de iodo urinario. Na sequencia foram submetidos a 131I em dose unica ambulatorial de 29,9 mCi e apos 12 meses a nova ecografia. Os grupos foram submetidos a analise estatistica considerando-se um nivel de significancia de 5%. Os grupos 1 e 2 foram estatisticamente semelhantes em relacao a dosagem de T3, T4, TSH, captacao de radioiodo na cintilografia e analise volumetrica. Nao houve diferenca na captacao pela cintilografia. A media de captacao de 131I pre tratamento no grupo 1 foi de 10%„b 3,16, e de 11,75% „b 2,80 apos a DPI. Nao observou-se um aumento na captacao do radioiodo apos a dieta ( p=0,15) Apos a dieta a dosagem do iodo urinario no grupo 1 foi igual ao grupo 2 (p> 0,05). Apos 12 meses da terapia com radioiodo nao houve diminuicao do volume tireoideano (p=0,97) e a media do volume final do grupo 1foi de 55,95„b 25,61ml e a media do grupo 2 foi de 56,56„b 44,14ml. Concluimos que a DPI orientada 15 dias antes da dose terapeutica, nao foi eficaz para aumento de captacao de radioiodo pela tireoide e reducao da concentracao de iodo urinario na populacao estudada. A dose de 29.9 mCi nao foi eficaz para reducao significativa do volume do BMN independentemente da quantidade de iodo na dieta.

Abstract: In the past decades, the low iodine diet has been used before radioactive iodine (131I) therapy trying to increase capture of radioactive iodine by the thyroid. Until now, however, no studies have demonstrated this correlation. The objective of this study is to analyse the capture of radioactive iodine after 131I therapy, the urinary iodine excretion and thyroid volume in patients with multi nodular goiter, utilizing, or not, an low iodine diet. Thirty patients with multi nodular goiter were assessed. Nine patiets were excluded. Twenty one patients were divided in two groups: group 1 (n=11), submitted to a low iodine diet (30 to 50 ƒÝg a day); and group 2 (n=10) submitted to a regular diet. Before the diet, were verified: T3, T4, TSH, volumetric analysis with ultrasound, cintilography and urinary iodine measurement. On the 15th day after the diet, they were analianalyzed through cintilography and urinary iodine. In sequence, they underwent 131I in a single ambulatory dose of 29.9mCi, and, after 12 months, a new ultrasound. The groups were submitted to statistical analysis considering a 5% significance level. Groups 1 and 2 were statistically similar in T3, T4, TSH levels, capture of radioactive iodine before and after diet and volumetric analysis before and after 131I dose. The capture of radioactive iodine after the low iodine diet in group 1 was not increased (p=0.15). The average 131I capture before diet was 10%„b3.16, and after the diet was 11.75%„b2.8. In group 2, submitted to a regular diet, there was also no diference of radioactive iodine capture before diet (8.93%„b2.73) and after diet (11.7%„b 4.63), p=0.10. After the diet, the levels of urinary iodine were similar in group 1 and group 2 (p<0,01). After 12 months of 131I therapy there was no decrease of thyroid volume (p=0.97). The average final volume in group 1 was 55.95„b25.61ml and in group 2 was 56.56„b44.14ml. In conclusion, in this population the low iodine diet 15 days before iodine therapy was not effective to increase the capture of radioactive iodine by the thyroid and also was not effective in reducing urinary iodine concentration. The 29.9mCi dose is not effective in reducing thyroid volume in patients with multinodular goiter, independent of the amount of iodine in the diet.