HORMONE ACTION

• Hormones act by 2 mechanisms:

  1. Direct gene activation - steroid hormones and thyroid hormone
  2. Second-messenger system - protein and peptide hormone
• Stimuli for Control of Hormone Release:

  • Hormonal - when endocrine organs are activated by other hormones
  • Humoral - when changing blood levels of certain ions and nutrients stimulate hormone release
  • Neural - when nerve fibers stimulate hormone release