AIM: As part of a longitudinal nutrition study of adolescents, changes in serum ferritin (s-Ft), serum transferrin receptors (s-TfR) and the TfR/Ft ratio from 15 to 21 y of age were studied in randomly selected Swedish adolescents.

METHODS: Blood samples from 60 males and 66 females were drawn at 15, 17 and 21 y of age.

RESULTS: In males, median s-Ft increased significantly from 33 microg l(-1) at 15 y to 96 microg l(-1) at 21 y, and in females, after a non-significant decrease at 17 y, from 27 at 15 y to 34 microg l(-1) at 21 y. Between 15 and 17 y, s-TfR increased significantly, in males from 5.9 to 7.7 microg l(-1), and in females from 5.2 to 7.6 microg l(-1), whereas s-TfR decreased significantly in both genders between 17 and 21 y. The log (TfR/Ft) ratio did not change in males between 15 and 17 y, but decreased significantly from 2.2 +/- 0.3 to 1.8 +/- 0.3 by the age of 21 y. In females, the TfR/Ft ratio increased significantly between 15 and 17 y, whereas a significant decrease was found by the age of 21 y. S-Ft <12 microg l(-1) at 15, 17 and 21 y was 3, 2 and 2% in males, and in females 18, 26 and 21%, respectively.

CONCLUSION: This study shows an increase in s-Ft and a decline in s-TfR in males, indicating increased iron stores. In females, s-Ft did not increase significantly, whereas s-TfR and the TfR/Ft ratio decreased between 17 and 21 y, indicating that cellular iron needs were met.