Intracrine

Intracrine refers to a hormone that acts inside a cell. Steroid hormones act through intracellular (mostly nuclear) receptors and are thus considered as intracrines. In contrast, peptide or protein hormones generally act as endocrines, autocrines or paracrines by binding to their receptors present on the cell surface. Several peptide/protein hormones or their isoforms also act inside the cell through different mechanisms. These peptide/protein hormones which have intracellular functions are also called intracrines. The term 'intracrine' is thought to be originally coined to represent peptide/protein hormones that also have intracellular actions.

The biological effects produced by intracellular actions are referred as intracrine effects while those produced by binding to cell surface receptors are called endocrine, autocrine or paracrine effects depending on the origin of the hormone. The intracrine effect of some of the peptide/protein hormones are similar to their endocrine, autocrine or paracrine effects; while these effects are different for some other hormones.