thyroxine

• what happens when the blood thyroxine level is lower than normal?

  the hypothalamus is stimulated to release thyrotropin releasing hormone, (TRH).
• what does TRH stimulate?

  stimulates the pituitary gland to release thyroid stimulating hormone (TSH).
• what does TSH stimulate?

  stimulates the thyroid gland to release thyroxine, so the blood thyroxine level rises back towards normal.
• what happens when the blood thyroxine level becomes higher than normal?

  the release of TRH from the hypothalamus is inhibited, which reduces the production of TSH, so the blood thyroxine level falls.
• what does a negative feedback system do in terms of thyroxine?

  keeps the amount of thyroxine in the blood at the right level.
• what does an underactive thyroid gland cause?

  weight gain because less thyroxine is produced so your metabolic rate drops. Meaning less of the glucose you take in gets broken down in respiration so more is stored as fat.
• what is your body's metabolic rate?

  the speed at which chemical reactions in the body occur.
• how does your body control the levels of hormones (and other substances) in the blood?

  negative feedback systems
• what is produced when the concentration of thyroxine in the blood is low?

  TRH (thyroptropin releasing hormone)
• what happens when TRH is produced?

  the pituitary gland releases TSH (thyroid stimulating hormone) which stimulates the secretion of thyroxine by the thyroid gland.
• what does TSH do?

  stimulates the secretion of thyroxine by the thyroid gland.
• what is TSH released by?

  the pituitary gland.
• what happens once the concentration of thyroxine in the blood has returned back to normal or above normal?

  TRH secretion is reduced which reduces TSH and thyroxine levels.
• what happens when TRH secretion is reduced?

  reduces TSH and thyroxine levels.
• what is produced if there is too little thyroxine in the body?


  TSH and TRH is produced