GCSE Combined Science (AQA)

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Thyroxine

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Homeostasis and Response Hormonal Coordination in Humans

Thyroxine

2:17 Negative Feedback Cycles
Spec 4.5.3.7
Previous Adrenaline Next Stages of the Menstrual Cycle
  • Thyroxine is a hormone produced by the thyroid gland located in the neck.
  • The pituitary gland, situated beneath the brain and known as the master gland, stimulates the thyroid gland to produce thyroxine.
  • Thyroxine regulates the basal metabolic rate, which is the rate of metabolism at rest.
  • It also plays a crucial role in the growth and development of various tissues and organs, including bones and the brain.
  • Thyroxine levels are controlled by a negative feedback mechanism:
  • Low thyroxine levels are detected by the brain.
  • The pituitary gland then releases thyroid-stimulating hormone (TSH).
  • TSH stimulates the thyroid to produce more thyroxine, increasing its levels.
  • High levels of thyroxine are detected by the brain, which then inhibits the release of TSH, causing thyroxine levels to decrease.
  • This cycle repeats to maintain balanced thyroxine levels.

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