Transient congenital hypothyroidism in Turkey: An analysis on frequency and natural course

Objective: prevalence of congenital hypothyroidism (ch) in turkey at birth was reported to be as high as 1:650 in 2008-2010. incidence rates of permanent and transient ch separately are unknown due to lack of follow-up data. we aimed to evaluate the impact of transient hypothyroidism on increasing incidence of ch and to determine the natural course and the clinical,biochemical,and imaging characteristics of transient ch. methods: baseline and follow-up data of the infants with ch detected at screening in six provinces in the black sea region were analyzed retrospectively during a time period covering the years 2008-2010. results: among 138 cases (48% female),16 (12%) showed transient hyperthyrotropinemia which resolved without intervention. of the treated 122 cases,63 (52%) had transient ch. while its frequency was 35% in 2008,it increased to 56% in 2009-2010,following a lowering of the thyroid stimulating hormone cutoff value. the frequency was higher in inland provinces than in coast (67% vs. 43%; p=0.01). clinical characteristics of permanent and transient cases were similar except femaleto- male sex ratios (1.5:1 vs. 0.6:1; p=0.02). l-thyroxine was discontinued in 70% of transient cases before 3 years of age at a median age of 19 (2-36) months. the only indication for early discontinuation of treatment was a low l-thyroxine dose,which was 1.25�0.27 �g/kg/day at withdrawal time. conclusion: our regional follow-up data showed that more than half of newborns with primary ch had transient thyroid dysfunction. in the majority of cases,discrimination between transient and permanent ch can be made before age 3 years,as indicated by cessation of l-thyroxine treatment. � journal of clinical research in pediatric endocrinology,published by galenos publishing.