Hormonal Adaptations in Professional Soccer Players: Ethnic Differences and Pathophysiological Mechanisms.

Professional soccer imposes substantial physiological demands eliciting complex neuroendocrine responses. This review synthesizes evidence on hormonal adaptations in professional soccer players, with emphasis on ethnic and national differences and underlying pathophysiological mechanisms. We analyzed 21 key studies investigating testosterone, cortisol, the testosterone-to-cortisol (T:C) ratio, growth hormone (GH), and insulin-like growth factor-1 (IGF-1) responses to training and competition. Acute cortisol elevations that may persist for up to 72 h post-match in some professional populations and T:C ratio reductions following congested fixture periods are reported across available studies, while somatotropic responses vary considerably across studies. Preliminary evidence suggests that ethnic and geographic background may influence circulating testosterone and urinary steroid excretion profiles, with UGT2B17 genetic polymorphisms identified as one contributing factor; however, the evidence base is limited and requires replication. Approximately 7.4% of elite junior cohorts-though not necessarily professional adult populations-develop non-functional overreaching (NFOR), characterized by blunted GH and ACTH responses. Pathophysiological mechanisms involve hypothalamic-pituitary--adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axis dysregulation producing anabolic-catabolic imbalance. Individualized, longitudinal T:C monitoring and post-match load moderation may be warranted; future research should establish ethnicity-specific normative values and investigate links between hormonal dysregulation and injury risk.