Growth Hormone Concentrations in Different Body Fluids Before and After Moderate Exercise

Area of Science:

• Exercise Physiology
• Endocrinology
• Biochemistry

Background:

• Growth hormone (GH) plays crucial roles in growth, repair, and immune function.
• Exercise-induced growth hormone response (EIGR) is a key physiological marker.
• Non-invasive sampling methods are sought for elite athletes due to aversion to venous sampling.

Purpose of the Study:

• To investigate the viability of urine and saliva samples as alternatives to blood for measuring GH concentration.
• To compare GH levels in serum, urine, and saliva following a standardized exercise protocol.

Main Methods:

• Eleven male participants (VO2peak 57.0 ± 6.0 mL·kg−1·min−1) exercised on a treadmill at 5% below their lactate threshold pace for 40 minutes.
• Blood, urine, and saliva samples were collected immediately before, and at 30 and 60 minutes after exercise.
• Concentrations of GH were analyzed across the different sample types.

Main Results:

• Salivary GH showed significant correlation with serum GH (p < 0.001), and urinary GH with serum GH (p < 0.05).
• Despite correlations, absolute GH concentrations varied significantly across serum, saliva, and urine.
• The distinct concentration profiles indicate different GH appearances in each compartment, complicating direct substitution.

Conclusions:

• Urinary and salivary GH measurements are not suitable substitutes for serum GH analysis in assessing exercise-induced changes.
• Consistent use of the same sample medium is essential for tracking EIGR patterns.
• Further research into compartmental GH exchange dynamics is warranted.