1 Division of Endocrinology, Children's Hospital of the District of Columbia
2 Division of Adolescent Medicine, Children's Hospital of the District of Columbia
3 The Department of Pediatrics, George Washington and Georgetown University Schools of Medicine, Washington, D.C.
The metabolism of radiothyroxine was studied in 10 normal euthyroid adolescent males, ranging in age from 13 to 18 years and at two stages of sexual maturation. The mean half-life for thyroxine in Stage 3 boys was 5.32 days, while that for Stage 5 boys was 5.82 days. The thyroxine half-life of the adolescent male is longer than that in the child (T
4.95 days) but is shorter than that in the young adult male (T
6.83 days). Some factor associated with age per se but not associated with the marked hormonal changes which occur at adolescence is responsible for the change in thyroxine half-life observed at this time.