Extrapineal

Extrapineal is an anatomical and physiological term used to describe tissues, sources, or processes that originate outside the pineal gland. The term is formed from the prefix ex- meaning outside and pineal, referring to the pineal gland, a small endocrine organ in the brain. In research and clinical contexts, extrapineal contrasts are drawn with intrapineal or pineal-derived sources.

In endocrinology, extrapineal melatonin production is a well-documented phenomenon. While the pineal gland is the central source of circadian melatonin in many species, several tissues outside the pineal gland synthesise melatonin locally, including the gastrointestinal tract, retina, skin, bone marrow, and immune cells. Extrapineal melatonin is thought to participate in local antioxidative and immunomodulatory signaling, and may contribute to overall circadian regulation.

The term is also used to describe tumors, cells, or lesions that originate outside the pineal region—i.e., extrapineal tumors or extrapineal neuroendocrine cells—contrasted with pineal-origin lesions.

Etymology: ex- Latin outside; pineal from pineal gland, named for its pinecone-like shape.