Resting Level of Insulin-Like Growth Factor-1 Is Not at Play in Cardiac Enlargement in Endurance-Trained Adolescents

PURPOSE: The study aimed to investigate resting levels of several selected growth and metabolic hormones in a group of 24 endurance-trained adolescents (aged 13-19 years) compared with 24 untrained age- and sex-matched controls, and to investigate if increased cardiac dimensions were related to these hormones at rest with emphasis on insulin-like growth factor-1 (IGF-1). METHODS: The hormones (cortisol, IGF-1, IGF-2, follicle-stimulating hormone, growth hormone, luteinizing hormone, prolactin, and thyroid-stimulating hormone) were analysed with chemiluminescence microparticle immunoassay (CMIA) or multiplex fluorochrome (Luminex) technique. Cardiac dimensions were assessed by echocardiographic examination at rest. Peak oxygen uptake was obtained by a maximal cardiopulmonary exercise test on a treadmill. RESULTS: Circulating levels of analysed hormones at rest did not differ between the groups. A correlation was found between increased cardiac dimensions and IGF-1 in the controls, but not in the active group. This correlation declined also among the controls when the cardiac parameters were indexed for body surface area. CONCLUSION: Increased cardiac dimensions in endurance-trained adolescents could not be related to resting levels of hormones associated with growth and metabolism, including IGF-1 and GH. In addition, the resting levels of these hormones seem not to be affected by intense regular endurance exercise in adolescents. These findings may contribute to the knowledge about cellular signaling that trigger growth as well as cardiac adaptation to endurance training in young athletes.