Introduction:Different growth and neuro-developmental outcomes have been associated with different doses of thyroxine given to infants with congenital hypothyroidism (CH).Materials and Methods:We studied the longitudinal growth pattern and assessed the neurodevelopment of 45 children with CH(25 girls, 20 boys) diagnosed through the national screening program in Qatar, for 6 years or more to examine the effects of initial T4 dosage (50 μg/day) with adjustment of T4 dose to maintain serum free T4 concentrations within the upper quartile of normal range and thyroid stimulating hormone < 4 mIU/mLThe birth size of newborns with CH diagnosed through the screening program before January 2003, was recorded and their growth in weight and stature was monitored every 3 months for at least 6 years of life. The IQ of children was assessed between 3 and 6 years of age using The Wechsler Preschool and Primary Scale of Intelligence (WPPSI-III).Results:Birth weight, length, and head circumference of patients (3.21 ± 0.43 kg, 50.5 ± 3.21 cm and 34.1 ± 1.5 cm, respectively) did not differ than those for 10,560 normal newborns with normal thyroid function (3.19 ± 0.59 kg, 50.5 ± 2.2 cm and 34.2 ± 1.7 cm). During the first year CH children growth (25.8 ± 2.8 cm/year) was similar to those for normal infants (25.5 ± 0.75 cm/year). During the first 6 years, stature growth was normal in all children with CH versus Center for disease control and prevention (CDC) data. The mean height standard deviation score (HtSDS) of children with CH showed adjustment (± 0.5 SD) toward their mid-parental height SDS (MPHtSDS) only during the second year of life. The children's mean HtSDS was higher by an average of 0.4 SD between the 2nd and 7th year of life.Conclusion:These data proved that effective screening and treatment completely assures normal neurodevelopment and linear growth in patients with CH. The data showed that their HtSDS slightly exceeds their MPHtSDS during childhood.