Intracrine

Intracrine refers to a hormone that acts inside a cell, regulating intracellular events.

Steroid hormones act through intracellular (mostly nuclear) receptors and, thus, may be considered to be intracrines.

In contrast, peptide or protein hormones, in general, act as endocrines, autocrines, or paracrines by binding to their receptors present on the cell surface.

Paracrine physiology has been understood for decades now and the effects of paracrine hormones have been observed when for example, an obesity associate tumor will face the effects of local adipocytes, even if it is not in direct contact with the fat pads in concern.

[1] Endocrine physiology on the other hand is a growing field and has had a new area explored, called intracrinology.