Usually the first gland that receives instructions is the pituitary gland. Pituitary hormones find their way through the blood to their target cells, which have special receptors that recognize a particular hormone. You could imagine each hormone as being a differently shaped key that will only fit into the correct receptor lock. The hormones then cause the target cells to behave in a certain way.
Have you heard the expression ‘fight or flight’? This refers to an instinctive response to stress or danger. Glands on the kidneys (adrenal glands)produce epinephrine, also known as adrenaline, that increases the heart rate and blood pressure, preparing the body to fight or flee.Doctors use epinephrine injections to treat severe allergic reactions. You may know someone who carries an ‘epi’ pen in case they are stung by a bee – that injection contains epinephrine.
Another part of the adrenal glands secretes corticosteroids, often just called steroids. These control things like the amount of salt in your body, how well you can fight off illness, and how quickly or slowly you burn energy.