Daily regulation of serum and urinary hepcidin is not influenced by submaximal cycling exercise in humans with normal iron metabolism

Does the TMPRSS6 C > T Polymorphism Modify the Endurance Training Effects on Hematological Parameters?

This study investigated the role of TMPRSS6 C > T polymorphism (TMPRP) on the effects of chronic aerobic training on main hematological parameters in male soccer referees, which is yet unknown. Two groups composed of total of 45 healthy male soccer referees and 42 sedentary were compared for hemogram, serum hepcidin, ferritin, and iron levels. TMPRP was determined from genomic DNA samples. Participants' physical and physiological (Yoyo endurance level-2 test) measurements were carried out. The athletic T carrier (Tc = TT + TC) group RBC count was significantly higher than the control (p < 0.01), whereas the athletic CC homozygous group serum iron and transferrin saturation (TS) were lower than the control depending on the TMPRP. The ferritin and iron values of the athletic Tc group were higher than of the athletic CC group (29.2% and 14.1%, respectively; p > 0.05) although the control Tc group RBC (p < 0.05) and iron (23.8%, p > 0.05) values were lower than the control CC due to genetic tendency. The training did not change hepcidin levels. These results suggest that the TMPRP can modify the endurance training effects on iron and TS levels and RBC count (in the CC and Tc groups) respectively. The CC group may be adversely affected for iron and TS from endurance trainings. It may be recommended that the training programs should be organized according to phenotype characteristics.

Effect of an acute exercise on early responses of iron and iron regulatory proteins in young female basketball players

Background

The accumulation of physiological stress and the presence of inflammation disturb iron management in athletes during intense training. However, little is known about the mechanisms regulating iron levels in athletes during training periods with low training loads. In the current study, we analyzed the effect of an acute exercise on early responses of iron and iron regulatory proteins at the end of such training periods.

Methods

The study was performed at the end of competitive phase of training. A total of 27 trained female basketball players were included in the study after application of the inclusion/exclusion criteria. The participants performed an incremental exercise on a treadmill. Blood samples were taken before the test, immediately after exercise, and after 3 h of restitution. Parameters, such as interleukin (IL) 6, hepcidin, ferritin, transferrin, hemopexin, and lactoferrin levels, total iron-biding capacity (TIBC), unsaturated iron-biding capacity (UIBC) were determined by using appropriate biochemical tests.

Results

The level of iron increased significantly after exercise, and then decreased within next 3 h restitution. Except for iron levels, only TIBC levels significantly increased after exercise and decreased to baseline level during rest period. No significant changes in the levels of hepcidin, IL-6, and other proteins related to the iron homeostasis were observed.

Conclusions

The increases in iron level after acute exercise is short-term and transient and appear to have been insufficient to induce the acute systemic effects in rested athletes.

Cancer Related Anemia: An Integrated Multitarget Approach and Lifestyle Interventions

Cancer is often accompanied by worsening of the patient's iron profile, and the resulting anemia could be a factor that negatively impacts antineoplastic treatment efficacy and patient survival. The first line of therapy is usually based on oral or intravenous iron supplementation; however, many patients remain anemic and do not respond. The key might lie in the pathogenesis of the anemia itself. Cancer-related anemia (CRA) is characterized by a decreased circulating serum iron concentration and transferrin saturation despite ample iron stores, pointing to a more complex problem related to iron homeostatic regulation and additional factors such as chronic inflammatory status. This review explores our current understanding of iron homeostasis in cancer, shedding light on the modulatory role of hepcidin in intestinal iron absorption, iron recycling, mobilization from liver deposits, and inducible regulators by infections and inflammation. The underlying relationship between CRA and systemic low-grade inflammation will be discussed, and an integrated multitarget approach based on nutrition and exercise to improve iron utilization by reducing low-grade inflammation, modulating the immune response, and supporting antioxidant mechanisms will also be proposed. Indeed, a Mediterranean-based diet, nutritional supplements and exercise are suggested as potential individualized strategies and as a complementary approach to conventional CRA therapy.

Association of Serum Hepcidin Levels with Aerobic and Resistance Exercise: A Systematic Review

BACKGROUND

Prevalence of iron deficiency is commonly reported among athletic population groups. It impairs physical performance due to insufficient oxygen delivery to target organs and low energy production. This is due to the high demand of exercise on oxygen delivery for systemic metabolism by the erythrocytes in the blood. Hepcidin, the key regulator of iron homeostasis, decreases to facilitate iron efflux into the circulation during enhanced erythropoiesis. However, acute anaemia of exercise is caused by increased hepcidin expression that is induced by stress and inflammatory signal. The study aimed to systematically review changes in serum hepcidin levels during resistance and aerobic exercise programmes.

METHODS

A systemic literature search from 2010 to April 2020 across seven databases comprised of Cochrane library, PubMed, Web of Science, Scopus, Embase, MEDLINE, and OpenGrey. The primary outcome was increased or decreased serum hepcidin from baseline after the exercise activity. Risks of bias were evaluated by using the National Institutes of Health (NIH) for quality assessment of before and after different exercise programmes.

RESULTS

Overall, twenty-three studies met the inclusion criteria. Out of the 23 studies, 16 studies reported significantly exercise-induced serum hepcidin elevation. Of the 17 studies that evaluated serum interleukin (IL)-6 levels, 14 studies showed significant exercise-induced serum IL-6 elevation. Changes in exercise-induced serum hepcidin and IL-6 levels were similar in both resistance and endurance exercise. Significant correlations were observed between post-exercise hepcidin and baseline ferritin levels (r = 0.69, p < 0.05) and between post-exercise hepcidin and post-exercise IL-6 (r = 0.625, p < 0.05).

CONCLUSION

Resistance and endurance training showed significant increase in serum hepcidin and IL-6 levels in response to exercise. Baseline ferritin and post-exercise IL-6 elevation are key determining factors in the augmentation of hepcidin response to exercise.

Acute effects of high-intensity exercise on hematological and iron metabolic parameters in elite male and female dragon boating athletes

OBJECTIVE

To investigate the acute effects of high-intensity exercise on blood hepcidin levels and other iron metabolic and hematological parameters in highly trained athletes of dragon boating as a sport performed in a sitting position.

METHODS

We conducted an exercise intervention study with a pre- and posttest blood measurement to determine the effects of high-intensity training on hematological and iron metabolic parameters in both male (n = 19) and female (n = 12) elite athletes of the German national dragon boating team. The study took place during the final training camp before the European championships. Blood samples were collected at baseline and 3 h after 3 consecutive high-intensity training bouts at the same day, each one lasting 1 h in duration.

RESULTS

After exercise, leukocytes, CPK, CKMB, and hepcidin levels increased significantly both in men and women. In contrast, iron concentrations decreased significantly. No gender-related differences were found. Compared with baseline, the postexercise concentrations of serum iron decreased significantly both in men [99.3 ± 46.3 to 61.2 ± 20.9 µg/dL (p < 0.001)] and in women [116.3 ± 34 to 67.1 ± 21.8 µg/dL (p < 0.001)] without a gender difference (p = 0.28). Hepcidin levels increased significantly both in men [9.1 ± 6.5 to 12.2 ± 5.8 ng/mL (p < 0.001)] and in women [8.0 ± 4.6 to 11.7 ± 5.7 ng/mL (p < 0.001)] without a significant gender difference in hepcidin changes (p = 0.34).

CONCLUSIONS

In conclusion, three consecutive high-intensity training bouts lead to elevated hepcidin levels and decreased iron levels in elite athletes of dragon boating. The increase in hepcidin levels may contribute to the risk of anemia in these athletes.

Effects of an Acute Exercise Bout on Serum Hepcidin Levels

Iron deficiency is a frequent and multifactorial disorder in the career of athletes, particularly in females. Exercise-induced disturbances in iron homeostasis produce deleterious effects on performance and adaptation to training; thus, the identification of strategies that restore or maintain iron homeostasis in athletes is required. Hepcidin is a liver-derived hormone that degrades the ferroportin transport channel, thus reducing the ability of macrophages to recycle damaged iron, and decreasing iron availability. Although it has been suggested that the circulating fraction of hepcidin increases during early post-exercise recovery (~3 h), it remains unknown how an acute exercise bout may modify the circulating expression of hepcidin. Therefore, the current review aims to determine the post-exercise expression of serum hepcidin in response to a single session of exercise. The review was carried out in the Dialnet, Elsevier, Medline, Pubmed, Scielo and SPORTDiscus databases, using hepcidin (and “exercise” or “sport” or “physical activity”) as a strategy of search. A total of 19 articles were included in the review after the application of the inclusion/exclusion criteria. This search found that a single session of endurance exercise (intervallic or continuous) at moderate or vigorous intensity (60–90% VO_2peak) stimulates an increase in the circulating levels of hepcidin between 0 h and 6 h after the end of the exercise bout, peaking at ~3 h post-exercise. The magnitude of the response of hepcidin to exercise seems to be dependent on the pre-exercise status of iron (ferritin) and inflammation (IL-6). Moreover, oxygen disturbances and the activation of a hypoxia-induced factor during or after exercise may stimulate a reduction of hepcidin expression. Meanwhile, cranberry flavonoids supplementation promotes an anti-oxidant effect that may facilitate the post-exercise expression of hepcidin. Further studies are required to explore the effect of resistance exercise on hepcidin expression.

The effect of 8-week different-intensity walking exercises on serum hepcidin, IL-6, and iron metabolism in pre-menopausal women

Objective

Hepcidin may be an important mediator in exercise-induced iron deficiency. Despite the studies investigating acute exercise effects on hepcidin and markers of iron metabolism, we found no studies examining the chronic effects of walking exercises (WE) on hepcidin and markers of iron metabolism in premenopausal women. The chronic effects of two 8-week different-intensity WE on hepcidin, interleukin 6 (IL-6), and markers of iron metabolism in pre-menopausal women were examined.

Methods

Exercise groups (EG) [moderate tempo walking group (MTWG), n = 11; brisk walking group (BWG), n = 11] walked 3 days/week, starting from 30 to 51 min. Control group (CG; n = 8) did not perform any exercises. BWG walked at ∼70%–75%; MTWG at ∼50%–55% of HRRmax. VO2max, hepcidin, IL-6, and iron metabolism markers were determined before and after the intervention.

Results

VO2max increased in both EGs, favoring the BWG. Hepcidin increased in the BWG (p < 0.01) and CG (p < 0.05). IL-6 decreased in the BWG and the MTWG (p < 0.05; p < 0.01). While iron, ferritin, transferrin, and transferrin saturation levels did not change in any group, total iron binding capacity (p < 0.05), red blood cells (p < 0.05), and hematocrit (p < 0.01) increased only in the BWG.

Conclusion

Both WE types may be useful to prevent inflammation. However, brisk walking is advisable due to the positive changes in VO2max and some iron metabolism parameters, which may contribute to prevent iron deficiency. The increase in hepcidin levels remains unclear and necessitates further studies.

Recent Advances in Iron Metabolism: Relevance for Health, Exercise, and Performance

Iron is necessary for physiological processes essential for athletic performance, such as oxygen transport, energy production, and cell division. However, an excess of "free" iron is toxic because it produces reactive hydroxyl radicals that damage biological molecules, thus leading to cell and tissue injury. Therefore, iron homeostasis is strictly regulated; and in recent years, there have been important advancements in our knowledge of the underlying processes. Hepcidin is the central regulator of systemic iron homeostasis and exerts its function by controlling the presence of the iron exporter ferroportin on the cell membrane. Hepcidin binding induces ferroportin degradation, thus leading to cellular iron retention and decreased levels of circulating iron. As iron is required for hemoglobin synthesis, the tight link between erythropoiesis and iron metabolism is particularly relevant to sports physiology. The iron needed for hemoglobin synthesis is ensured by inhibiting hepcidin to increase ferroportin activity and iron availability and hence to make certain that efficient blood oxygen transport occurs for aerobic exercise. However, hepcidin expression is also affected by exercise-associated conditions, such as iron deficiency, anemia or hypoxia, and, particularly, inflammation, which can play a role in the pathogenesis of sports anemia. Here, we review recent advances showing the relevance of iron for physical exercise and athletic performance. Low body iron levels can cause anemia and thus limit the delivery of oxygen to exercising muscle, but tissue iron deficiency may also affect performance by, for example, hampering muscle oxidative metabolism. Accordingly, a hemoglobin-independent effect of iron on exercise capacity has been demonstrated in animal models and humans. Here, we review recent advances showing the relevance of iron for physical exercise and athletic performance.

Joint Model of Iron and Hepcidin During the Menstrual Cycle in Healthy Women

Hepcidin regulates serum iron levels, and its dosage is used in differential diagnostic of iron-related pathologies. We used the data collected in the HEPMEN (named after HEPcidin during MENses) study to investigate the joint dynamics of serum hepcidin and iron during the menstrual cycle in healthy women. Ninety menstruating women were recruited after a screening visit. Six fasting blood samples for determination of iron-status variables were taken in the morning throughout the cycle, starting on the second day of the period. Non-linear mixed effect models were used to describe the evolution of iron and hepcidin. Demographic and medical covariates were tested for their effect on model parameters. Parameter estimation was performed using the SAEM algorithm implemented in the Monolix software. A general pattern was observed for both hepcidin and iron, consisting of an initial decrease during menstruation, followed by a rebound and stabilising during the second half of the cycle. We developed a joint model including a menstruation-induced decrease of both molecules at the beginning of the menses and a rebound effect after menses. Iron stimulated the release of hepcidin. Several covariates, including contraception, amount of blood loss and ferritin, were found to influence the parameters. The joint model of iron and hepcidin was able to describe the fluctuations induced by blood loss from menstruation in healthy non-menopausal women and the subsequent regulation. The HEPMEN study showed fluctuations of iron-status variables during the menstrual cycle, which should be considered when using hepcidin measurements for diagnostic purposes in women of child-bearing potential.

Effects of resistance exercise on iron absorption and balance in iron-deficient rats

We have previously reported that resistance exercise improved the iron status in iron-deficient rats. The current study investigated the mechanisms underlying this exercise-related effect. Male 4-week-old rats were divided into a group sacrificed at the start (week 0) (n = 7), a group maintained sedentary for 6 weeks (S) or a group that performed exercise for 6 weeks (E), and all rats in the latter groups were fed an iron-deficient diet (12 mg iron/kg) for 6 weeks. The rats in the E group performed climbing exercise (5 min × 6 sets/day, 3 days/week). Compared to the week 0 rats, the rats in the S and E groups showed lower tissue iron content, and the hematocrit, hemoglobin, plasma iron, and transferrin saturation values were all low. However, the tissue iron content and blood iron status parameters, and the whole body iron content measured using the whole body homogenates of the rats, did not differ between the S group and the E group. The messenger RNA (mRNA) expression levels of hepcidin, duodenal cytochrome b, divalent metal transporter 1, and ferroportin 1 did not differ between the S group and the E group. The apparent absorption of iron was significantly lower in the E group than in the S group. Therefore, it was concluded that resistance exercise decreases iron absorption, whereas the whole body iron content is not affected, and an increase in iron recycling in the body seems to be responsible for this effect.

Hepcidin and sports anemia

Iron is an important mineral element used by the body in a variety of metabolic and physiologic processes. These processes are highly active when the body is undergoing physical exercises. Prevalence of exercise-induced iron deficiency anemia (also known as sports anemia) is notably high in athletic populations, particularly those with heavy training loads. The pathogenesis of sports anemia is closely related to disorders of iron metabolism, and a more comprehensive understanding of the mechanism of iron metabolism in the course of physical exercises could expand ways of treatment and prevention of sports anemia. In recent years, there have been remarkable research advances regarding the molecular mechanisms underlying changes of iron metabolism in response to physical exercises. This review has covered these advances, including effects of exercise on duodenum iron absorption, serum iron status, iron distribution in organs, erythropoiesis, and hepcidin’s function and its regulation. New methods for the treatment of exercise-induced iron deficiency are also discussed.

A seven day running training period increases basal urinary hepcidin levels as compared to cycling

Background

This investigation compared the effects of an extended period of weight-bearing (running) vs. non-weight-bearing (cycling) exercise on hepcidin production and its implications for iron status.

Methods

Ten active males performed two separate exercise training blocks with either running (RTB) or cycling (CTB) as the exercise mode. Each block consisted of five training sessions (Day 1, 2, 4, 5, 6) performed over a seven day period that were matched for exercise intensity. Basal venous blood samples were obtained on Day 1 (D1), and on Recovery Days 3 (R3) and 7 (R7) to assess iron status, while basal and 3 h post-exercise urinary hepcidin levels were measured on D1, D2, D6, as well as R3 and R7 (basal levels only) for each condition.

Results

Basal urinary hepcidin levels were significantly elevated (p ≤ 0.05) at D2, R3 and R7 as compared to D1 in RTB. Furthermore, 3 h post-exercise urinary hepcidin levels on D1 were also significantly higher in RTB compared to CTB (p ≤ 0.05). In CTB, urinary hepcidin levels were not statistically different on D1 as compared to R7. Iron parameters were not significantly different at D1 compared to R3 and R7 during both conditions.

Conclusions

These results suggest that basal hepcidin levels may increase over the course of an extended training program, especially if a weight-bearing exercise modality is undertaken. However, despite any variations in hepcidin production, serum iron parameters in both RTB and CTB were unaffected, possibly due to the short duration of each training block. In comparing running to cycling, non-weight-bearing activity may require more training sessions, or sessions of extended duration, before any significant changes in basal hepcidin levels appear. Chronic elevations in hepcidin levels may help to explain the high incidence of iron deficiency in athletes.

Repeated "all out" interval exercise causes an increase in serum hepcidin concentration in both trained and untrained men

This investigation assessed effects of high-intensity interval exercise (HIE; triple Wingate anaerobic test) on inflammatory markers, iron metabolism and hepcidin concentrations. Group of highly trained judo athletes (TR) and non-trained control males (CG) completed a triple Wingate test separated by 4.5min rest. Venous blood samples were collected before, immediately after, 1h, 24h, and 5days following exercise and analysed for serum of IL-6, IL-10, iron, and ferritin. Physiological response to exercise was also determined. Concentration of IL-6 and hepcidin increased 1h after exercise in both groups (p<0.05). Hepcidin returned post testing 24h in TR, whereas in CG it remained elevated during 5days following exercise. Changes in hepcidin did not correlate with shifts in serum IL-6, iron and ferritin concentrations. Gathered data suggest that following HIE, hepcidin increased independently of IL-6 and neither blood nor storage iron affected this phenomena.

Serum hepcidin levels and muscle iron proteins in humans injected with low- or high-dose erythropoietin

Inhibition of hepcidin expression by erythropoietic signals is of great physiological importance; however, the inhibitory pathways remain poorly understood. To investigate (i) the direct effect of erythropoietin (Epo) and (ii) the contribution of putative mediators on hepcidin repression, healthy volunteers were injected with a single dose of Epo, either low (63 IU/kg, n = 8) or high (400 IU/kg, n = 6). Low-dose Epo provoked hepcidin down-modulation within 24 h; the effect was not immediate as hepcidin circadian variations were still present following injection. High-dose Epo induced no additional effect on the hepcidin response, that is hepcidin diurnal fluctuations were not abolished in spite of extremely high Epo levels. We did not find significant changes in putative mediators of hepcidin repression, such as transferrin saturation, soluble transferrin receptor, or growth differentiation factor 15. Furthermore, the potential hepcidin inhibitor, soluble hemojuvelin, was found unaltered by Epo stimulation. This finding was consistent with the absence of signs of iron deficiency observed at the level of skeletal muscle tissue. Our data suggest that hepcidin repression by erythropoietic signals in humans may not be controlled directly by Epo, but mediated by a still undefined factor.

Exercise-induced changes in iron status and hepcidin response in female runners

Background and Aims

Exercise-induced iron deficiency is a common finding in endurance athletes. It has been suggested recently that hepcidin may be an important mediator in this process.

Objective

To determine hepcidin levels and markers of iron status during long-term exercise training in female runners with depleted and normal iron stores.

Methods

Fourteen runners were divided into two groups according to iron status. Blood samples were taken during a period of eight weeks at baseline, after training and after ten days’ recovery phase.

Results

Of 14 runners, 7 were iron deficient at baseline and 10 after training. Hepcidin was lower at recovery compared with baseline (p<0.05). The mean cell haemoglobin content, haemoglobin content per reticulocyte and total iron binding capacity all decreased, whereas soluble transferrin receptor and hypochromic red cells increased after training and recovery (p<0.05 for all).

Conclusion

The prevalence of depleted iron stores was 71% at the end of the training phase. Hepcidin and iron stores decreased during long-term running training and did not recover after ten days, regardless of baseline iron status.

Interleukin-6 contributes to hepcidin mRNA increase in response to exercise

The iron regulatory peptide hormone hepcidin has been proposed to participate in training-induced iron deficiency. Plasma and urinary hepcidin increase in response to one bout of prolonged exercise, a condition also known to increase plasma interleukin-6 (Il-6). Because Il-6 activates hepcidin transcription and expression during inflammation, our aim was to study the role of this cytokine in hepatic hepcidin mRNA expression during exercise and recovery. We used a rodent model of exhaustive running exercise, where rats were treated or not with cyclosporin A (CsA), a calcineurin inhibitor shown to blunt plasma Il-6 during exercise. Despite similar running intensity and duration, animals treated with CsA had 50% lower plasma Il-6 concentrations at the end of exercise. The concomitant rise in hepatic mRNA levels of two Il-6 responsive genes, suppressor of cytokine signaling (SOCS) 3 and Il-6 receptor alpha, was blunted in CsA-treated group. Finally, hepcidin mRNA levels increased in response to exercise, peaking 2h later, but peak values were significantly lower in CsA group compared to control group. This result strongly suggests that plasma Il-6 is involved in exercise-induced increase of hepcidin gene expression.

Hepcidin in human iron disorders: diagnostic implications

BACKGROUND

The peptide hormone hepcidin plays a central role in regulating dietary iron absorption and body iron distribution. Many human diseases are associated with alterations in hepcidin concentrations. The measurement of hepcidin in biological fluids is therefore a promising tool in the diagnosis and management of medical conditions in which iron metabolism is affected.

CONTENT

We describe hepcidin structure, kinetics, function, and regulation. We moreover explore the therapeutic potential for modulating hepcidin expression and the diagnostic potential for hepcidin measurements in clinical practice.

SUMMARY

Cell-culture, animal, and human studies have shown that hepcidin is predominantly synthesized by hepatocytes, where its expression is regulated by body iron status, erythropoietic activity, oxygen tension, and inflammatory cytokines. Hepcidin lowers serum iron concentrations by counteracting the function of ferroportin, a major cellular iron exporter present in the membrane of macrophages, hepatocytes, and the basolateral site of enterocytes. Hepcidin is detected in biologic fluids as a 25 amino acid isoform, hepcidin-25, and 2 smaller forms, i.e., hepcidin-22 and -20; however, only hepcidin-25 has been shown to participate in the regulation of iron metabolism. Reliable assays to measure hepcidin in blood and urine by use of immunochemical and mass spectrometry methods have been developed. Results of proof-of-principle studies have highlighted hepcidin as a promising diagnostic tool and therapeutic target for iron disorders. However, before hepcidin measurements can be used in routine clinical practice, efforts will be required to assess the relevance of hepcidin isoform measurements, to harmonize the different assays, to define clinical decision limits, and to increase assay availability for clinical laboratories.

Early effects of erythropoietin on serum hepcidin and serum iron bioavailability in healthy volunteers

Hepcidin regulates plasma iron bioavailability and subsequently iron availability for erythropoiesis. rHuEPO has been reported to decrease hepcidin expression in case of repeated subcutaneous injections. Thus, hepcidin level measurement could be a candidate marker for detection of rHuEPO abuse. However, when used for doping, rHuEPO can be injected intravenously and the scheme of injection is unknown. Our aim was to evaluate the early effects of a single intravenous rHuEPO injection on serum hepcidin levels. Fourteen male healthy volunteers received one intravenous injection of 50 U/Kg of rHuEPO during a placebo-controlled, randomized, double-blind, cross-over study. Serum hepcidin, quantified by a competitive ELISA method and iron parameters was then evaluated for 24 h. Serum levels of hepcidin were significantly increased 4 h after rHuEPO injection when compared with placebo injection (78.3 ± 55.5 vs. 57.5 ± 34.6 ng/ml, respectively; +36%, p < 0.05), whereas iron and transferrin saturation dramatically decreased 12 h after rHuEPO injection when compared with placebo injection (9.2 ± 3.5 vs. 15.8 ± 4.2 μg/l, respectively; -42%, p < 0.05 and 14.8 ± 5.0 vs. 26.3 ± 6.4%, respectively; -44%, p < 0.05). In addition, 12 and 24 h after rHuEPO injection serum hepcidin levels were lower compared with placebo injection (41.6 ± 27.4 vs. 56.6 ± 28.1 ng/ml after 12 h; -27%, p < 0.05 and 26.0 ± 29.6 vs. 81.2 ± 29.4 ng/ml after 24 h; -68%, p < 0.05). Intravenous injection of recombinant EPO induces a precocious and transient increase of serum hepcidin leading to a transient decrease of iron bioavailability. The transitory increase and dynamics of its concentration make difficult the practical use of hepcidin to detect rHuEPO doping.