The correct answer is hormones.
Hormones are signaling molecules which are produced by glands and transported by the circulatory system to the target organs. The functions of the hormone are very diverse, they regulate physiology and behavior. Hormones have different chemical structures, eicosanoids, steroids, and amino acid/protein derivatives. The hormones can be the part of the endocrine signaling system (transported via blood). or produced by cells that affect the same cell (autocrine or intracrine signaling) or nearby cells (paracrine signaling).
