A hormone is any member of a class of signaling molecules in multicellular organisms, that are transported to distant organs to regulate physiology and / or behavior. Hormones are required for the correct development of animals, plants and fungi. The lax definition of a hormone means that many different classes of molecule can be defined as hormones. Among the substances that can be considered hormones, are eicosanoids, steroids, amino acid derivatives, protein / peptides and gases.
