Paracrine signaling is a form of cell-to-cell communication in which a substance, known as a paracrine factor, binds to receptors on the target cell’s surface and initiates an intracellular response. Paracrine signaling occurs at short distances between cells, usually within 1 mm or less. In contrast to endocrine (long distance) and autocrine (self) signaling, paracrine signals are not secreted into the bloodstream but instead diffuse out into the local environment where they exert their effects on nearby cells.

The process by which this occurs begins with the release of the paracrine factors from an initial source cell. This can be done either through exocytosis or through secretion via gap junctions. Once released into its surrounding environment, it can bind to receptors on other cells that are close enough for it to reach them. Upon binding to these receptors, a signal transduction cascade will begin within the target cell leading to activation of specific pathways that lead to various cellular responses such as proliferation or differentiation depending on what type of receptor was activated and what its downstream effectors are.