Endocrine System and Exercise Metabolism

Key Glands and Hormones

1. Anterior Pituitary Gland

   • Releases hormones stimulated by the hypothalamus.
   • Growth Hormone:
     • Builds tissues and organs.
     • Promotes muscle hypertrophy and fat metabolism.
     • Increases blood-free fatty acids, allowing for higher fat utilization and glucose sparing.
     • Release proportional to exercise intensity.

2. Thyroid Gland

   • Releases Tri-iodothyronine (T3) and Thyroxine (T4).
   • Increases metabolic rates, protein synthesis, glucose uptake, glycolysis, gluconeogenesis, and free fatty acid availability.
   • Enhances aerobic metabolism by increasing mitochondria number and size.

3. Adrenal Glands (Medulla and Cortex)

   • Adrenal Medulla:

     • Releases Epinephrine (80%) and Norepinephrine (20%).
     • Stimulates heart rate, contractility, blood pressure, respiration, and metabolism.
     • Increases glycogenolysis and free fatty acid availability.
     • Supports blood flow redistribution to active muscles.

   • Adrenal Cortex:

     • Releases corticosteroid hormones, focusing on Glucocorticoids (e.g., Cortisol).
     • Increases gluconeogenesis, free fatty acid availability, and protein catabolism.
     • Reduces glycolysis to spare glucose for the brain.
     • Anti-inflammatory effects during exercise.

4. Pancreas

   • Controls blood glucose levels.

   • Insulin:

     • Released during high blood glucose levels.
     • Facilitates glucose entry into cells, glycogen synthesis, protein and fat synthesis, decreases lipolysis, and gluconeogenesis.

   • Glucagon:

     • Released during low blood glucose levels.
     • Increases glucose release from the liver, glycogenolysis, and gluconeogenesis.

Impact on Metabolism

• Hormones regulate carbohydrate and fat metabolism during exercise.
• Balance between glucose and fat usage is critical to sustain the energy needs of the body.
• Important to consider the timing and intensity of exercise to understand hormonal responses.

Additional Notes

• Cortisol release is significant after 30 minutes of moderate to intense aerobic exercise.
• Insulin decreases during exercise; more information can be found in another resource.