PURPOSE: The aim of the study was to investigate how 8-week strength training affects adolescent athletes' basal hormone concentrations, sex hormone binding globulin (SHBG), insulin-like growth factor binding protein-3 (IGFBP-3), cytokine, and oxidative stress markers. METHODS: Twenty adolescent handball players participated in this study. The participants were randomly divided into the strength training group (ST, n = 10) and the control group (C, n = 10). ST participates in strength training 3 sessions a week for 8 weeks and C participates only in handball training. We quantified serum basal hormone concentration, SHBG, IGFBP3, oxidative stress markers, and IL-6 in each subject's blood samples before and after 8 weeks of strength training. RESULTS: Interestingly, while insulin-like growth factor-1 (IGF-1) concentration declined in group C (p <
0.05), it did not in ST (p >
0.05). Furthermore, the basal concentration of growth hormone (GH), total testosterone (T), cortisol (Cor), total antioxidant status (TAS), and serum-free androgen index (FAI) basal concentration did not change in ST and C. Basal IGFBP-3 and SHBG concentrations decreased only in ST (p <
0.05), but not in C (p >
0.05). Serum-free testosterone (FT) levels increased in ST and C (p >
0.05). Total oxidant status (TOS) and oxidative stress index (OSI) reduced ST and C (p <
0.05). Serum interleukin-6 (IL-6) levels did not alter groups ST and C. CONCLUSION: Strength training did not affect basal serum concentrations of T, GH, IGF-1, COR, IL-6, and TAS, but it caused a decrease in SHBG and IGFBP3 concentrations in ST. Increased basal FT concentration and improved serum TOS may not depend on strength training.