Hormones are substances that act upon target or effector cells after being secreted. After theyve been synthesized they remain active for a while and are then destroyed by the body. Their degradation is necessary because hormonal activity must only be temporary.
The chemical structure of a hormone and its specific type of receptor will determine the way it acts; thats why there are many different types of hormones.
Protein or protein derived hormones
Although they circulate through the blood, they do not act immediately. They are stored until they are needed; in the meantime, they bind to the receptors of the outer membrane of a cell.
This group of protein or protein derived hormones is secreted by the pituitary gland, parathyroid glands (parathyroid hormone), placenta and the pancreas.
Steroids
When the body needs them, an enzyme is activated within the cells and manufacturing begins. After being synthesized, they pass through the cell membrane, bind to their receptor and enter the bloodstream. This hormone is secreted by the suprarenal cortex and gonads.
