In recent years there has been a remarkable enhancement in the knowledge and understanding of endocrine responses to exercise and exercise training in children and adolescents who participate in sports. This includes, for example, exercise-associated changes in growth factors that regulate muscle adaptations to exercise training, the use of hormonal changes to assess training intensity, as well as deleterious effects of competitive sports, in particularly if associated with inadequate nutrition, on growth and the reproductive system. However, major scientific gaps still exist in our understanding of the application and translation of this knowledge to the everyday use of young athletes and their coaches. These gaps include the translation of laboratory research to "real-life" training setting to optimize training efficiency, mainly due to the lack of "real-life" exercise studies; and the use of genetic endocrinology for sports selection, the prediction of excellence in sports and to improve training.