Lecture Notes: Growth Hormone Functioning

Overview

• Purpose of Growth Hormone (GH):
  • Controls muscle functions including glucose consumption.
  • Stimulates fat metabolism in the liver.
  • Influences growth in body tissues and kidneys.
  • Does not control growth in the brain and eyes.

Hypothalamus and Growth Hormone Release

• Hypothalamus Control:

  • The hypothalamus controls the release of growth hormone.
  • It releases either GHIH (Growth Hormone Inhibitory Hormone) or GHRH (Growth Hormone Releasing Hormone).

• GHIH:

  • Inhibits the anterior pituitary to stop body growth when suppression is required.

• GHRH:

  • Released in response to stress, fasting, or exercise.
  • Stimulates the anterior pituitary to release growth hormone.

Action of Growth Hormone

• Target Site:

  • Anterior pituitary is targeted, not the posterior pituitary.
  • Growth hormone released from the anterior pituitary.

• Secondary Targets:

  • Liver:

    • Releases IGF-1 and IGF-2 (Insulin Growth Factors 1 and 2).
    • IGFs bind to body tissues and bones to stimulate metabolism, growth, and bone lengthening.

  • Direct Binding:

    • GH directly binds to sites promoting growth and metabolism.

Metabolic Processes

• cAMP Production:
  • Increase in cAMP production accompanies GH release.
  • Stimulates metabolism processes like glucose uptake and fat metabolism.
  • Enhances muscle glucose uptake.

Regulation of Growth Hormone

• Feedback Mechanism:
  • Hypothalamus acts as a detector of hormone levels.
  • When GH is sufficient, the hypothalamus releases GHIH to inhibit further GH release.
  • When conditions demand, GHRH is released initiating a cascade of GH release and subsequent metabolic effects.

Key Physiological Responses

• Increase in metabolism.
• Body growth and hyperplasia.
• Stimulation of fat metabolism.
• Involvement of cAMP in growth hormone functioning.

Conclusion

• This lecture provided an overview of the mechanisms and regulation of growth hormone.
• Next lecture will delve deeper into specific aspects of growth hormone activity.