Quantification of testosterone‐dependent erythropoiesis during male puberty

New findings What is the central question of this study? To what extent does testosterone influence hemoglobin formation during male puberty? What is the main finding and its importance? In boys, testosterone might be responsible for about 65% of the increase in hemoglobin mass during puberty. The underlying mechanisms are assumed to be twofold: (i) indirectly, mediated by the increase in LBM, and (ii) directly by immediate testosterone effects on erythropoiesis. Thereby, an increase in testosterone by 1ng/ml is associated with an increase in Hbmass by ∼65g. These processes are likely to determine endurance performance in adulthood. Abstract The amount of hemoglobin 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 hemoglobin mass (Hbmass) in both male and female children and adolescents and to evaluate the possible influences of altitude and training. Three-hundred thirteen differently trained boys and girls aged from 9 to 18 years and living at altitudes of 1000m and 2600m 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. Hemoglobin 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 (373±88g vs 498±77g) and by 95% in boys, (428±95g vs 832±143g) respectively. This difference can most likely be attributed to indirect testosterone influences through an increase in LBM and to direct testosterone effects on erythropoiesis, which increase the Hbmass by ∼65g per 1ng/ml. Altitude and training statuses were not associated with testosterone, but with an increase in Hbmass (altitude by 1.1g/kgLBM, training by 0.8 g/kgLBM). 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. This article is protected by copyright. All rights reserved.