title: Congenital Hypothyroidism: Optimal Initial Dosage and Time of Initiation of Treatment: A Systematic Review.
abstract: BACKGROUND
  Appropriate management of neonates, tested positive for congenital hypothyroidism (CH), in particular, the initial dosage of levothyroxine and the time of initiation of treatment is a critical issue. The aim of this study was to assess all current evidence available on the subject to ascertain the optimal initial dose and optimal initiation time of treatment for children with CH.
  
  
  METHODS
  In this study, all published research related to the initiation treatment dose and the onset time of treatment in congenital hypothyroidism were reviewed. The searched electronic databases included Medline, Science direct, Scopus EMBASE, PsycINFO, Cochrane, BIOSIS and ISI Web of Knowledge. Additional searches included websites of relevant organizations, reference lists of included studies, and issues of major thyroid and pediatrics journals published within the past 35 years. Studies were included if they were written in English and investigated levothyroxine dose or timing of treatment or both, used for the treatment of children with congenital hypothyroidism.
  
  
  RESULTS
  Two thousand three hundred and seventy-four articles (excluding duplicates) were retrieved from the primary search. After reviewing the titles, abstracts and full-texts of studies, eventually, 22 studies were found that met our inclusion criteria. Amongst these, 17 and 12 evaluated outcomes of different treatment doses and treatment timing, respectively. Overall, the majority of these studies emphasized the initial high dose of levothyroxine and early treatment of newborns with hypothyroidism. There were, however, some studies that disagreed with increasing levothyroxine dose at initiation of treatment.
  
  
  CONCLUSIONS
  Considering the results of this review, apparently there is no difference in opinion regarding the early initiation of treatment, whereas determining the optimal dose of levothyroxine for start of treatment in CH patients still remains a controversial issue, demonstrating the need for further studies, despite the fact that use of high doses can lead to rapid normalization of biochemical indices, although this may cause complications.
authors.affiliation: Department of Epidemiology, School of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, IR Iran.
authors.forename: Khaled
authors.initials: K
authors.lastname: Rahmani
authors.affiliation: Assistant Professor of Endocrinology, Department of Endocrinology and Metabolism, Ministry of Health, Tehran, IR Iran.
authors.forename: Shahin
authors.initials: S
authors.lastname: Yarahmadi
authors.affiliation: Assistant Professor of Epidemiology, Department of Epidemiology, Shahid Beheshti University of Medical Sciences, Tehran, IR Iran.
authors.forename: Koorosh
authors.initials: K
authors.lastname: Etemad
authors.affiliation: Assistant Professor of Endocrinology, Department of Endocrinology and Metabolism, Ministry of Health, Tehran, IR Iran.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Koosha
authors.affiliation: Professor of Biostatistics, Department of Epidemiology, School of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, IR Iran.
authors.forename: Yadollah
authors.initials: Y
authors.lastname: Mehrabi
authors.affiliation: NCD Expert, Department of Endocrinology and Metabolism, Ministry of Health, Tehran, IR Iran.
authors.forename: Nasrin
authors.initials: N
authors.lastname: Aghang
authors.affiliation: Safety Promotion and Injury Prevention Research Center, School of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, IR Iran.
authors.forename: Hamid
authors.initials: H
authors.lastname: Soori
keywords: Congenital Hypothyroidism; Review Article; Starting Treatment Dose; Treatment Initiation Timing