Comparativa de los métodos de evComparativa de los métodos de evaluación de la reserva de yodo corporal previamente a la realización de tratamiento con radioyodoaluación de la reserva de yodo corporal previamente a la realización de tratamiento con radioyodo / Comparison of Body Iodine Pool Assessment Methods Before Radioiodine Therapy

Introducción y objetivos: El tratamiento con yodo radiactivo (RAIT) se recomienda para reducir el riesgo de recurrencia y de metástasis en personas con cáncer diferenciado de tiroides (CDT) de riesgo intermedio-alto. En la preparación para la RAIT, la estimulación de la tirotropina y la reducción en la reserva corporal de yodo son elementos importantes para contribuir al éxito de la terapia. Para ello, se pide a los pacientes que reduzcan la ingesta de este mineral antes de la RAIT, y puede evaluarse su reserva corporal midiendo su excreción por la orina (yoduria) antes del tratamiento. El objetivo de nuestro estudio ha sido comparar los métodos utilizados para medir la reserva de yodo corporal en la evaluación de la eficacia de la dieta con bajo contenido en yodo (RID) aplicada a la preparación del paciente para la RAIT. Pacientes y métodos: Suspendieron la levotiroxina tres semanas antes de la RAIT y fueron controlados con una RID durante las dos semanas previas a la realización del tratamiento 80 pacientes con CDT. Tras dos semanas de RID, en todos se llevó a cabo una recolección de orina de 24h el día previo a la fecha de administración de la RAIT. Los sujetos finalizaron dicha recolección en la mañana de la fecha de RAIT y suministraron una muestra puntual de orina. Se calculó la excreción estimada de creatinina en orina de 24 horas de los pacientes. La estimación de la excreción urinaria de yodo o yoduria (UIE) de 24 horas oras se determinó a partir del índice yodo/creatinina (I/C) obtenido en la muestra de orina puntual de los individuos. Se compararon los resultados de la yoduria de 24 horas, la concentración de yodo en la muestra puntual de orina, el cociente I/C en la muestra puntual de orina y la estimación de la yoduria de 24 horas en los pacientes. Resultados: En 99%, la eficacia de la RID fue suficiente según la yoduria de 24 horas obtenida previamente a la RAIT...(AU)

Introduction and Objectives: Radioactive iodine therapy (RAIT) is recommended to reduce the risk of recurrence and metastasis in patients with intermediate-high risk differentiated thyroid cancer (DTC). In preparation for RAIT, stimulation of thyroid-stimulating hormone and reduction of body iodine pool are important for treatment success. For this purpose, patients are asked to reduce their iodine intake before RAIT, and the body iodine pool can be evaluated by measuring iodine excretion in urine before treatment. The aim of our study is to compare the methods used to measure the body iodine pool in the evaluation of the restricted iodine diet (RID) effectiveness applied in the RAIT preparation. Patients and methods: Eighty DTC patients discontinued levothyroxine three weeks before RAIT and followed up with a RID two weeks before treatment. After two weeks of RID, all patients collected their 24-hour urine the day before the RAIT date. Patients completed 24-hour urine samples on the morning of the RAIT date and also provided a spot urine sample. The estimated 24-hour creatinine excretion of the patients was calculated. Estimated 24-hour urinary iodine excretion (UIE) was calculated using the spot urine iodine/creatinine (I/C) ratio of the patients. 24-hour UIE, iodine concentration in spot urine, I/C ratios in spot urine and estimated 24-hour UIE of the patients were analyzed by comparing with each other. Results: In 99% of the patients, RID efficiency was sufficient according to 24-hour UIE before RAIT. The mean 24-hour UIE was 48.81 micrograms/day (mcg/day) in 24-hour urine samples taken from the patients to evaluate the body iodine pool. The patients’ iodine concentrations in spot urine, I/C ratios in spot urine, and estimated 24-hour UIE were all statistically significantly lower than actual 24-hour UIE, which was the reference method (p: 0.026 vs <0.001 vs 0.041)..... (AU)

Comparison of body iodine pool assessment methods before radioiodine therapy.

INTRODUCTION AND OBJECTIVES: Radioactive iodine therapy (RAIT) is recommended to reduce the risk of recurrence and metastasis in patients with intermediate-high risk differentiated thyroid cancer (DTC). In preparation for RAIT, stimulation of thyroid-stimulating hormone and reduction of body iodine pool are important for treatment success. For this purpose, patients are asked to reduce their iodine intake before RAIT, and the body iodine pool can be evaluated by measuring iodine excretion in urine before treatment. The aim of our study is to compare the methods used to measure the body iodine pool in the evaluation of the restricted iodine diet (RID) effectiveness applied in the RAIT preparation. PATIENTS AND METHODS: Eighty DTC patients discontinued levothyroxine three weeks before RAIT and followed up with a RID two weeks before treatment. After two weeks of RID, all patients collected their 24-h urine the day before the RAIT date. Patients completed 24-h urine samples on the morning of the RAIT date and also provided a spot urine sample. The estimated 24-h creatinine excretion of the patients was calculated. Estimated 24-h urinary iodine excretion (UIE) was calculated using the spot urine iodine/creatinine (I/C) ratio of the patients. 24-h UIE, iodine concentration in spot urine, I/C ratios in spot urine and estimated 24-h UIE of the patients were analyzed by comparing with each other. RESULTS: In 99% of the patients, RID efficiency was sufficient according to 24-h UIE before RAIT. The mean 24-h UIE was 48.81 micrograms/day (mcg/day) in 24-h urine samples taken from the patients to evaluate the body iodine pool. The patients' iodine concentrations in spot urine, I/C ratios in spot urine, and estimated 24-h UIE were all statistically significantly lower than actual 24-h UIE, which was the reference method (p: 0.026 vs <0.001 vs 0.041). Moderate positive correlation between 24-h UIE and iodine concentration in spot urine (r: 0.440), I/C ratio in spot urine (r: 0.493), and estimated 24-h UIE (r: 0.560) found. The strongest correlation was obtained with the estimated 24-h UIE. CONCLUSION: The estimated 24-h UIE obtained by using the I/C ratio in spot urine can be used practically and safely as an alternative to UIE in 24-h urine, which is the gold standard method for evaluating body iodine pool.

Challenges in the evaluation of urinary iodine status in pregnancy: the importance of iodine supplement intake and time of sampling.

OBJECTIVES: Median urinary iodine concentration (UIC) is the recommended method to evaluate iodine status in pregnancy, but several factors may challenge the interpretation of the results. We evaluated UIC in pregnant women according to (1) sampling in the hospital versus at home, (2) time of the most recent iodine supplement intake prior to sampling, and (3) members of their household. STUDY DESIGN: Danish cross-sectional study in the year 2012. Pregnant women (n = 158), their male partners (n = 157) and children (n = 51) provided a questionnaire with detailed information on iodine supplement intake and a spot urine sample obtained in the hospital and/or at home for measurement of UIC and urinary creatinine concentration. RESULTS: In the pregnant women providing a urine sample both in the hospital and at home (n = 66), individual UIC (p = 0.002) and urinary creatinine concentration (p = 0.042), but not estimated 24-hour urinary iodine excretion (p = 0.79), were higher when sampling was at home. Median UIC was dependent on the time of the most recent iodine supplement intake prior to sampling [same day (n = 79): 150 µg/l (95% CI 131-181 µg/l), the day before (n = 51): 105 µg/l (78-131 µg/l), several days ago/non-user (n = 28): 70 µg/l (56-94 µg/l), p < 0.001]. The pattern was similar in the male partners. Apart from a more frequent iodine supplement intake in pregnancy (87.3% vs. partners 15.9%), no systematic differences were observed in urinary measurements between the pregnant women and their partners. CONCLUSIONS: Time of spot urine sampling and time span from iodine supplement intake to spot urine sampling should be considered when evaluating urinary iodine status in pregnancy.