Source: Plasma Membrane; Public Domain: http://commons.wikimedia.org/wiki/File:CellMembraneDrawing.jpg
A class of hormones that are primarily derived from proteins and are water soluble due to their polar nature; steroid hormones are transported freely through the blood. Non-steroid hormones interact with receptors on the cell membrane and activate secondary messenger systems that carry out their effects within the cell.
A group of signaling molecules located near a hormone receptor on the inside of the cell; when a non-steroid hormone binds to its receptor it activates secondary messenger systems that carry out specific effects inside of the cell. Non-steroid hormones rely on secondary messenger signaling molecules because they are unable to penetrate the cell membrane and get into the cell.
Hormones that have a cholesterol backbone and are not soluble in water due to their lipid structure; steroid hormones are transported through the blood attached to carrier proteins. Steroid hormones penetrate the cell membrane and interact with nuclear receptors that affect DNA transcription.