Variation of soluble transferrin receptor and ferritin concentrations in human serum during recovery from exercise

Serum soluble transferrin receptor (sTfR) has been proposed as a more stable index of iron status than serum ferritin in athletes. However, the variation in sTfR concentration during recovery from acute exercise is unknown. The aim of the present study was to examine the effect of prolonged moderate exercise on ferritin and sTfR concentrations, as well as on several hematologic variables up to 24 h post-exercise. Fifteen young, untrained men exercised on a cycle ergometer for 45 min at a heart rate of 150-155 beats min(-1) and provided blood samples before as well as immediately, 6 h, and 24 h after exercise. Ferritin and sTfR values did not change significantly with time. sTfR levels exhibited lower variation during the observation period, the median intra-individual coefficient of variation being 5.2%, as opposed to 10.9% for ferritin. In conclusion, serum ferritin concentration is not affected by prolonged moderate exercise and can be used as a reliable index of iron status, at least for athletes not involved in extreme physical activities. Serum sTfR concentration seems to be more stable and could replace ferritin as the preferred index of iron stores if problems associated with the novelty of the assay were overcome.