• Most hormones are regulated by feedback mechanisms.
  • A feedback mechanism is a loop in which a product feeds back to control its own production.
  • Negative feedback keeps the concentration of a hormone within a narrow range.
  • This type of feedback brings things back to normal whenever they start to become too extreme.Positive feedback is much less common because it causes conditions to become increasingly extreme.
  • The thyroid gland is a good example of this type of regulation.
  • It is controlled by the negative feedback loop shown in Figure below.
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