Influence of Initial Levothyroxine Dose on Neurodevelopmental and Growth Outcomes in Congenital Hypothyroidism

Evaluation of Long-term Benefit-risk Profile of Levothyroxine Treatment in Children With Congenital Hypothyroidism: Influence of Initial Levothyroxine Dose on Neurodevelopmental, Growth, Cardiovascular and Skeletal Outcomes

The primary objective of this study is to evaluate the risk-benefit profile of long-term treatment of two different initials treatment schemes with L-T4 on the neurodevelopmental and auxological outcomes in children with congenital hypothyroidism, diagnosed by neonatal screening in order to find the best dose of initial thyroid hormone replacement to assure the best long-term developmental outcome without any adverse effects on auxological, cardiovascular and skeletal outcomes. The secondary objective of the study is to evaluate the role of other factors that, in addition to the initial L-T4 therapy,can influence long-term neurodevelopmental and auxological outcomes as well as the cardiovascular system and bone metabolism outcomes.

Seventy-two neonates detected by the neonatal screening program for congenital hypothyroidism were randomly assigned to receive one of the two initial L-T4 replacement dose: Group A received an initial replacement dose of 10-12.5 mcg/kg/die and Group B received an initial replacement dose of 12.6-15 mcg/kg/die. The adequacy of treatment were monitored closely by clinical evaluation and regular measurement of FT4 and TSH. Cognitive development were evaluated through the Griffiths Mental Development Scales at the the age of 2 yeas. Cognitive and behavioural assessment at the age of 4 years were performed using the Wechsler Preschool and Primary scale of Intelligence. Growth were evaluate at the enrolment and at each visit. Skeletal maturation were evaluated at diagnosis and at the age of 1 and 4 years. At the age of 4 years a quantitative ultrasound measurements and cardiovascular evaluation were performed.

Inclusion Criteria:

• Congenital Hypothyroidism diagnosed by neonatal screening program
• Age less than 30 days at diagnosis
• TSH value at confirmatory diagnosis above 30 mU/l
• Caucasian ethnicity

Exclusion Criteria:

• Prematurity
• Major congenital malformations
• Neonatal diseases
• Chromosomopathies
• Known maternal thyroid diseases