The amount of haemoglobin during puberty is related to endurance performance in adulthood. During male puberty, testosterone stimulates erythropoiesis and could therefore be used as a marker for later endurance performance. This cross-sectional study aimed to determine the relationship between serum testosterone concentration and haemoglobin mass (Hbmass) in both male and female children and adolescents and to evaluate the possible influences of altitude and training. Three-hundred and thirteen differentially trained boys and girls aged from 9 to 18 years and living at altitudes of 1000 and 2600 m above sea level entered the study. The stage of sexual maturation was determined according to the classification of Tanner. Testosterone was measured by ELISA. Hbmass was determined by CO-rebreathing. Haemoglobin concentration did not change during maturation in girls and was 11% higher during puberty in boys, while Hbmass was elevated by 33% in Tanner stage V compared to stage II in girls (498 ± 77 vs. 373 ± 88 g) and by 95% in boys (832 ± 143 vs. 428 ± 95 g). This difference can most likely be attributed to indirect testosterone influences through an increase in lean body mass (LBM) and to direct testosterone effects on erythropoiesis, which increase the Hbmass by ∼65 g per 1 ng/ml. Altitude and training statuses were not associated with testosterone, but with an increase in Hbmass (altitude by 1.1 g/kg LBM, training by 0.8 g/kg LBM). Changes in Hbmass are closely related to testosterone levels during male puberty. Further studies will show whether testosterone and Hbmass during childhood and adolescence can be used as diagnostic tools for endurance talents.

<p class="p1"><strong>Antecedentes.</strong> La investigación sobre los efectos de la exposición a la altura sobre la eritropoyesis y el metabolismo de hierro ha permitido conocer el comportamiento y las adaptaciones que se presentan en poblaciones residentes o expuestas a diversas alturas sobre el nivel del mar.</p><p class="p1"><strong>Objetivo.</strong> El presente artículo de revisión tiene como objetivo analizar la información científica disponible y actualizar al lector respecto al efecto de la altura sobre los indicadores de la eritropoyesis y el metabolismo del hierro.</p><p class="p1"><strong>Materiales y métodos.</strong> Se realizó una búsqueda de artículos de diferentes bases de datos como PubMed, MEDLINE, Scielo, EBSCO y OVID, la cual se hizo con base en los títulos médicos MeSH (Medical Subjects Headings) y DeCS Bireme (descriptores de la salud).</p><p class="p1"><strong>Resultados.</strong> A nivel de la eritropoyesis se puede observar un incremento de la eritropoyetina y de los reticulocitos con el incremento en la altura. En el metabolismo del hierro se puede apreciar un descenso de las reservas del hierro (ferritina) y un incremento de la transferrina y del receptor soluble de transferrina con ascenso en la altitud. </p><p class="p1"><span class="s1"><strong>Conclusión.</strong> La magnitud de estos incrementos depende del tiempo de exposición a la hipoxia, el género y la población, ya que se han encontrado diferencias entre etnias que viven a la misma altura pero presentan diferencias en las adaptaciones. Las investigaciones existentes están referidas a grandes alturas, pero en alturas intermedias por debajo de los 2600 m s. n. m. todavía existen grandes interrogantes.</span></p>

Introduction: To a considerable extent, the magnitude of blood volume (BV) and hemoglobin mass (Hbmass) contribute to the maximum O2-uptake (VO2max), especially in endurance-trained athletes. However, the development of Hbmass and BV and their relationships with VO2max during childhood are unknown. The aim of the present cross-sectional study was to investigate Hbmass and BV and their relationships with VO2max in children and adolescents. In addition, the possible influence of endurance training and chronic hypoxia was evaluated.Methods: A total of 475 differently trained children and adolescents (girls n = 217, boys n = 258; untrained n = 171, endurance trained n = 304) living at two different altitudes (∼1,000 m, n = 204, ∼2,600 m, n = 271) and 9–18 years old participated in the study. The stage of puberty was determined according to Tanner; Hbmass and BV were determined by CO rebreathing; and VO2max was determined by cycle ergometry and for runners on the treadmill.Results: Before puberty, there was no association between training status and Hbmass or BV. During and after puberty, we found 7–10% higher values in the trained groups. Living at a moderate altitude had a uniformly positive effect of ∼7% on Hbmass in all groups and no effect on BV. The VO2max before, during and after puberty was strongly associated with training (pre/early puberty: boys +27%, girls +26%; mid puberty: +42% and +45%; late puberty: +43% and +47%) but not with altitude. The associated effects of training in the pre/early pubertal groups were independent of Hbmass and BV, while in the mid- and late pubertal groups, 25% of the training effect could be attributed to the elevated Hbmass.Conclusions: The associated effects of training on Hbmass and BV, resulting in increased VO2max, can only be observed after the onset of puberty.

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Introduction: Living at high altitude increases oxidative stress. Likewise, growth and maturation during adolescence can increase levels of reactive oxygen species (ROS). Changes in redox profiles have been evaluated in adults living at high altitudes; however, there are no studies on these changes in peripubertal populations living at moderate altitudes, we determine how living at moderate altitude affects the oxidative and inflammatory status of healthy preadolescents and adolescents. Materials and Methods: A cross-sectional study was conducted in healthy male Colombian preadolescents and adolescents (9–18 years old, Tanner scale classification) who lived at low altitude (n = 26) or moderate altitude (n = 26). Plasma oxidative and inflammatory status was assessed via spectrophotometry. Oxidative markers included malondialdehyde, 4-hydroxy-trans-2-nonenal, and carbonyl groups. Antioxidant markers included total antioxidant status, glutathione, catalase, superoxide dismutase, uric acid, and thiols. Inflammatory markers included interleukins-1, -6, and -10 and tumor necrosis factor. Results: Only uric acid levels were higher in adolescents (5.34 and 5.66 mg/dl) compared to preadolescents (3.85 and 4.07 mg/dl) in both moderate and low altitude groups, respectively. Participants who lived at moderate altitude presented significantly higher levels of malondialdehyde (4.82 and 3.73 nM/mg protein) and lower level of glutathione and thiols (1.21 and 1.26 μmol/mg protein) than in those at low altitude. Their inflammatory profiles did not differ. Conclusion: Oxidant profiles increased in peripubertal populations residing at moderate altitude; this could be owing to antioxidant consumption by ROS and active metabolism during puberty.