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Endocrine Care: Marlies J. E. Kempers, Liesbeth van der Sluijs Veer, Ria W. G. Nijhuis-van der Sanden, Caren I. Lanting, Libbe Kooistra, Brenda M. Wiedijk, Bob F. Last, Jan J. M. de Vijlder, Martha A. Grootenhuis, and Thomas Vulsma Neonatal Screening for Congenital Hypothyroidism in The Netherlands: Cognitive and Motor Outcome at 10 Years of Age J Clin Endocrinol Metab 2007; 92: 919-924 [Abstract] [Full text] [PDF]

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Severe congenital hypothyroidism: treating at 20 days of life is not early enough

Guy Van Vliet   (30 May 2007)

Severe congenital hypothyroidism: treating at 20 days of life is not early enough 30 May 2007
Guy Van Vliet, M.D. University of Montreal Send letter to journal: Re: Severe congenital hypothyroidism: treating at 20 days of life is not early enough guy.van-vliet{at}recherche-ste-justine.qc.ca Guy Van Vliet	I have read with interest the paper by Kempers et al. (1) comparing the cognitive and motor outcome at 10 years of age of two cohorts of children with congenital hypothyroidism born in the Netherlands in 1981-1982 and 1992-1993. The two groups differed by the age at which treatment was started (28 vs. 20 days). Because the authors found a similar loss of IQ points in the subgroups of children with severe hypothyroidism, they conclude that advancing the age at treatment within this time frame does not improve outcome. The authors themselves underline that the treatment practices have changed since 1993. Specifically, a randomized controlled trial documented that a starting dose of 14.5 µg/kg.d thyroxine is necessary to normalize TSH within 2 weeks and also results in better intellectual outcome at 5 years (2). This contrasts with the 6-8 µg/kg.d used in the two Dutch cohorts reported by Kempers et al (1). It is noteworthy that in another Dutch cohort born in 1993-1996, the development of infants with severe congenital hypothyroidism was normal, provided they were treated before 13 days with more than 9.5 µg/kg.d (3). Even if one accepts the conclusions of Kempers et al. (1), they should not lead to complacency in the management of screening programs. In fact, there are a number of arguments that every day of delay in treatment may lead to loss of intellectual potential for children with severe congenital hypothyroidism.. In 1989, Vulsma et al. (4) published a landmark study showing that there was substantial transplacental transfer of thyroxine but that this maternal thyroxine was cleared from the neonate’s circulation in 8-19 days. So, as soon as the umbilical cord is cut, this protective mechanism disappears and the clock starts ticking. Fisher (5) has estimated that IQ may decrease by several points per week and that this loss may be non-linear, with the most impact during the early weeks of life. We have also argued that, in order for other neonatal screening procedures (such as screening for congenital adrenal hyperplasia) to achieve their primary objectives, the results should be available by 7 days of age (6). The physiological data mentioned above and clinical sense command that, notwithstanding the results of Kempers et al. (1), we aim for treating neonates with severe congenital hypothyroidism as early as possible. For this purpose, screening programs have to be continuously audited to achieve the shortest possible turnaround time. References 1. Kempers MJ, van der Sluijs Veer L, Nijhuis-van der Sanden RW, Lanting CI, Kooistra L, Wiedijk BM, Last BF, de Vijlder JJM, Grootenhuis MA, Vulsma T. 2007. Neonatal screening for congenital hypothyroidism in the Netherlands: cognitive and motor outcome at 10 years of age. J Clin Endocrinol Metab 92:919-924 2. Selva KA, Harper A, Downs A, Blasco PA, Lafranchi SH. 2005. Neurodevelopmental outcomes in congenital hypothyroidism: comparison of initial T4 dose and time to reach target T4 and TSH. J Pediatr 147:775-780 3. Bongers-Schokking JJ, Koot HM, Wiersma D, Verkerk PH, de Muinck Keizer-Schrama SM. 2000. Influence of timing and dose of thyroid hormone replacement on development in infants with congenital hypothyroidism. J Pediatr 136:292-297 4. Vulsma T, Gons MH, de Vijlder JJ. 1989. Maternal-fetal transfer of thyroxine in congenital hypothyroidism due to a total organification defect of thyroid agenesis. N England J Med 321:13-16 5. Fisher DA. 2000. The importance of early management in optimizing IQ in infants with congenital hypothyroidism. J Pediatr 136:273-274 6. Van Vliet G, Czernichow P. 2004. Screening for neonatal endocrinopathies: rationale, methods and results. Semin Neonatol 9:75-85