Enhanced coupling within gonadotropic and adrenocorticotropic axes by moderate exercise in healthy men

Context: Exercise elicits incompletely defined adaptations of metabolic and endocrine milieu, including the gonadotropic and corticotropic axes. Objective: To quantify the impact of acute exercise on coordinate luteinizing hormone (LH) and testosterone (T) and adrenocorticotropic hormone (ACTH) and cortisol secretion in healthymen in relation to age. Participants and Design: Prospectively randomized, within-subject crossover study in 23 men aged 19 to 77 years old. Subjects underwent rest and 30 minutes of mixed exercise at 65% of maximal aerobic capacity with 10-minute blood sampling between 7:00 AM and 1:00 PM, 2 weeks apart. Main Outcome Measures: Incremental changes in LH, T, ACTH, and cortisol concentrations, the feedforward and feedback strength between exercise and rest, quantified by approximate entropy (ApEn), and bihormonal synchrony, quantitated by cross-ApEn. Results: Mean hourly exercise-minus-rest LH and ACTH increments increased from 20.055 6 0.187 to 0.755 6 0.245 IU/L (P = 0.003) and from 2.9 6 2.2 to 71.2 6 16.1 ng/L (P < 0.0001), respectively, during exercise. T and cortisol increments increased concurrently from 29.6 6 16.7 to 47.6 6 17.1 ng/dL (P < 0.0001) and 0.45 6 0.76 to 7.27 6 0.64 mg/dL (P < 0.0001), respectively. During exercise, feedforward and feedback LH-T and ACTH-cortisol cross-ApEn decreased markedly quantifying enhanced hormonal coupling. Conclusions: Acute moderate mixed exercise in healthy men rapidly enhances feedforward LH-T and ACTH-cortisol coordination and reciprocal feedback within the gonadotropic and corticotropic axes. In principle, enhancement of both LH-T and ACTH-cortisol secretory synchrony by exercise could reflect augmented coupling between brain-testicular and brain-adrenal neural outflow.