This study examined the hypothesis that exercise-induced changes in circulating testosterone would be centrally mediated via hypothalamic-pituitary release of luteinizing hormone (LH). We tested this hypothesis by examining overnight LH, total and free testosterone (TT and FT), and cortisol (C) concentrations in 10 young healthy men (21 ± 1 yr) during two experimental sessions: a control and an acute heavy-resistance exercise bout (50 total sets consisting of squats, bench press, leg press, and latissimus dorsi pull-down). Exercise was performed from 1500 to 1700, and blood sampling began at 1700 and continued until 0600 the next morning. Blood was sampled every 10 min for LH and every hour for TT, FT, and C. Hormonal concentrations were determined via RIA, and the secretion characteristics of LH were analyzed with deconvolution analysis. When overnight postexercise concentrations were compared with control concentrations, no statistically significant (P  0.05) differences were observed for LH half-life, LH pulse frequency, interpulse interval, pulse amplitude, or pulse mass. Significant differences were observed for LH production rate (13.6 ± 4 and 17.9 ± 5 IU · l distribution volume¹ · day¹ for exercise and control, respectively, a 24% reduction). For the ANOVA marginal main effect means due to condition, C was significantly elevated (5.9 ± 0.7 vs. 4.0 ± 0.4 µg/dl), while TT (464 ± 23 vs. 529 ± 32 ng/dl) and FT (15.6 ± 0.7 vs. 18.3 ± 0.9 pg/ml) were significantly decreased for the exercise condition. These data demonstrate that the decline in overnight testosterone concentrations after acute heavy-resistance exercise is accompanied by a blunted LH production rate and elevated C concentrations.