HORMONES 2003, 2(2):103-112 Research paper The influence of exercise on growth hormone and testosterone in prepubertal and early-pubertal boys Charilaos Tsolakis 1 , Paraskevi Xekouki 2 , Socratis Kaloupsis 1 , Dimitrios Karas 1 , Dimosthenis Messinis 1 , George Vagenas 1 , Athanasios Dessypris 3 1 Department of Physical Education and Sports Science, Athens University, 2 Endocrine unit, First Dept of Pediatrics Athens University School of Medicine, 3 Department of Biochemistry and Molecular Biology, Athens University, School of Biology, Athens, Greece ABSTRACT The purpose of this study was two fold a) to determine the levels of hormonal parameters which are related to growth and sexual maturation (T, SHBG, FAI, GH) in 66 pre-pubertal and early-puber- tal boys (11-13 years old) who systematically engage in individual and team sports activities of endurance, strength, speed and skill, respectively, and b) to investigate the effect of two different forms of exercise namely aerobic (AG) and weight training (WG) on androgen levels in 19 seden- tary pre-pubertal boys. The control groups (CG) consisted of boys of the same age who attended only the school physical education programmes. The individuals included in the study participated voluntarily after their parents had been informed and had given their written consent. Hormonal concentrations were determined using radioimmunoassay and immunoradiometric assays. No dif- ferences were observed among the various athletes groups as regards Tanner stages, height and weight. The mean T and FAI values of the control group did not differ from those of the correspond- ing athletes group. Significant differences were observed among the groups regarding BMI, % body fat, T, SHBG, FAI and GH (p<0.05). T and FAI values in the WG group were significantly higher than the corresponding concentrations: a) in the AG group by 338 and 609%, p<0.05 and b) in the control group CG by 91 and 96%, p<0.05, respectively. The hormonal differences detected among the various groups of athletes must be attributed as much to the type of physical exercise and to developmental factors as to the selection criteria used for the different athletic talents. The impor- tance of the specificity of training stimulus in the hormonal adaptations of pre-pubertal sedentary subjects was demonstrated. Key words: sports, Testosterone, GH, physiological adaptations. INTRODUCTION The huge growth in the popularity of sports among youth over the last two decades has led to childrens participation in them at ever younger ages, and in training programmes of increased intensity and pro- longed duration, resulting in various effects on the rate of physical growth and maturity 1,2 . The athletic talent selection is made according to Address correspondence and requests for reprints to: Tsolakis Charilaos Ph.D, 6 Kotsika str., e-mail: tsolakis@phed.uoa.gr Received 16-12-02, Revised 21-02-03, Accepted 13-03-03