Thyroxine is produced from the thyroid gland, which stimulates the basal metabolic rate. It controls the speed at which oxygen and food products react to release energy for the body to use. Thyroxine plays an important role in growth and development. Thyroxine levels are controlled by negative feedback.
Adrenaline is produced by the adrenal glands in times of fear or stress. It targets vital organs, increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for 'flight or fight'. Adrenaline is not controlled by negative feedback.
When adrenaline is released into the bloodstream it creates multiple effects:
The effects of adrenalin allow the body to prepare for action in situations where a quick response may be essential.