Hormones are chemical messengers that act as a communication system between different cells and organs in the body. They are released by endocrine glands and travel through the bloodstream to target cells, where they bind to specific receptors and influence the cells’ behaviour. Hormones can influence a target cell in many ways, including changing its metabolism, stimulating gene expression, and activating or inhibiting biochemical pathways. They also play an important role in regulating growth and development, as well as fertility and reproduction.