Abstract
A competitive protein-binding method was used to determine serum thyroxine concentration throughout childhood, adolescence, and in young adults. The values showed a gradual decrease as the child became older and reached adult levels by the time of adolescence. The range (mean +/- 2 SD mug/100 ml) for cord serum was 8.8-14.8; for 4 weeks to 11 years, 6.5-13.9; for 11 to 17 years, 5.4-12.2, and for young adults 6.0-11.2.