[Normal thyroid-stimulating hormone levels in screening for congenital hypothyroidism in newborn twins]. / Valores normales de TSH en el cribado neonatal del hipotiroidismo congénito en nacimientos gemelares.

INTRODUCTION: A large number of articles have been published since neonatal screening for congenital hypothyroidism (CH) started in the 1970s. Surprisingly, little information on false negative results in these screenings has been reported. PATIENTS AND METHODS: Thyroid-stimulating hormone (THS) levels were determined in 360,651 newborn infants in Malaga until March 2005. One hundred and fifty-six CH cases were detected, of which 86 % were permanent and 14 % were transient. In this study, we retrospectively analyzed a group of 13 CH dizygotic twins in which only one of the twins had CH. RESULTS: The first two patients were diagnosed late and data on whether they were included in neonatal screening were lacking. In seven of the 13 patients, TSH values were initially normal: five patients were diagnosed by a second test performed 14 days after birth and were treated before they were 1 month old, and two were diagnosed and treated late because a second test was not performed. In the remaining four patients, TSH values were initially elevated but were lower than confirmation test values. CONCLUSIONS: It is now widely accepted that thyroid function could be compensated between two dizygotic twins if only one of the twins has CH, leading to a false negative result. The results of the present study indicate the need to repeat the test for CH 14 days after birth in all dizygotic twins.

Valores normales de TSH en el cribado neonatal del hipotiroidismo congénito en nacimientos gemelares / Normal thyroid-stimulating hormone levels in screening

Introducción A pesar del gran número de trabajos publicados desde que, en la década de 1970, se implantaron los programas de cribado neonatal para el diagnóstico del hipotiroidismo congénito, no hay demasiados datos sobre resultados paradójicos o casos que pudieran escapar del cribado. Pacientes y métodos Hasta marzo de 2005, en Málaga se ha estudiado la hormona tiroestimulante (TSH) en 360.651 recién nacidos detectándose 156 hipotiroidismos congénitos, de los que 86 % fueron permanentes y 14 % transitorios. En este trabajo se analiza, retrospectivamente, un grupo de 13 hipotiroidismos congénitos nacidos de parto gemelar, en los que solamente uno de los hermanos ha tenido la enfermedad. Resultados Los dos primeros fueron diagnosticados tarde y se desconoce si se estudiaron en el cribado. En 7 casos la TSH dio un valor normal: cinco, diagnosticados mediante una segunda muestra realizada a los 14 días, se trataron antes de un mes de vida; a dos no se repitió la prueba, iniciando tarde el tratamiento. Los cuatro restantes tuvieron desde la primera prueba un valor elevado de TSH, siendo significativamente inferior al obtenido para su confirmación. Conclusiones En la actualidad se acepta que la función tiroidea pueda estar compensada entre los dos gemelos, resultando un falso negativo en el caso de ser uno de ellos hipotiroideo congénito. De los datos que se presentan se deduce la necesidad de repetir la prueba a los 14 días en todos los nacimientos gemelares

Introduction A large number of articles have been published since neonatal screening for congenital hypothyroidism (CH) started in the 1970s. Surprisingly, little information on false negative results in these screenings has been reported. Patients and methods Thyroid-stimulating hormone (THS) levels were determined in 360,651 newborn infants in Malaga until March 2005. One hundred and fifty-six CH cases were detected, of which 86 % were permanent and 14 % were transient. In this study, we retrospectively analyzed a group of 13 CH dizygotic twins in which only one of the twins had CH. Results The first two patients were diagnosed late and data on whether they were included in neonatal screening were lacking. In seven of the 13 patients, TSH values were initially normal: five patients were diagnosed by a second test performed 14 days after birth and were treated before they were 1 month old, and two were diagnosed and treated late because a second test was not performed. In the remaining four patients, TSH values were initially elevated but were lower than confirmation test values. Conclusions It is now widely accepted that thyroid function could be compensated between two dizygotic twins if only one of the twins has CH, leading to a false negative result. The results of the present study indicate the need to repeat the test for CH 14 days after birth in all dizygotic twins