[Course of serum levels of free thyroid hormones in children from 10 days to 2 years of age]. / Evolution des taux sériques d'hormones thyroidiennes libres chez l'enfant de 10 jours à 2 ans.

We have been studying a population of 95 normal children aged 10 days to 2 years, in order to determine the normal values of free thyroid hormone in this class of age. The concentrations were measured by radioimmunoassay (Lepetit system). Free T3 (FT3) appears remarkably stable, with a mean at 4,92 pg/ml (3,23 - 7,50 mg/ml at +/- 2SD). These concentrations are significantly higher than those of adult. Free T4 (FT4) shows a significant decrease over the first month of life, with a mean at 14,31 pg/ml (10,27 - 19,94 pg/ml at +/- 2SD). There is no significant variation between the age of one month and 2 years. The mean is 10,51 pg/ml (7,00 - 15,79 pg/ml +/- 2SD).