Hormone pathway: Metabolism

• Thyroxine- regulates metabolism. Ensures that cells have sufficient energy for various functions 
• Stimulus: low levels of thyroxine (T4) and triiodothyronine (T3) in the blood
• Hypothalamus: releases Thyrotropin - releasing hormone (TRH)
• TRH stimulates the pituitary to release thyroid stimulating hormone (TSH)
• Thyroid Gland: TSH promotes the thyroid gland to produce and release more T3  and T4 
• Hypothalamus: signals posterior pituitary to release antidiuretic hormone (ADH) into the bloodstream
• Kidneys: ADH increases the permeability of the collecting ducts, promoting water reabsorption
• Response: Elevated levels of T4 and T3 in the bloodstream
• Feedback: high levels of T4 and T3 inhibit further releases of TRH and TSH
• This reduces stimulation of the thyroid gland