Thyroxine

• Thyroxine:

  • Hormone released by the thyroid gland, which is found in the neck
  • Plays an important role in regulating the basal metabolic rate - speed at which chemical reactions in the body occur while the body is at rest
  • Also important for loads of processes in the body, such as stimulating protein synthesis for growth and development
• • Thyroxine is released in response to thyroid stimulating hormone (TSH) which is released from the pituitary gland
• Negative feedback

  • A negative feedback system keeps the amount of thyroxine in the blood at the right level
• Negative feedback

  • When the level of thyroxine in the blood is higher than normal, the secretion of TSH from the pituitary gland is inhibited (stopped)
  • This reduces the amount of thyroxine released from the thyroid gland, so the level in the blood falls back towards normal
• Negative feedback

  • When the level of thyroxine in the blood is lower than normal, the secretion of TSH from the pituitary gland is stimulated (started up) again
  • This increases the amount of thyroxine released from the thyroid gland, so the level in the blood rises back towards normal