Adrenal Glands var addthis_config = {"data_track_addressbar":true};

Adrenal Glands are a Tyranid Biomorph common amongst front-line Tyranid creatures. Small organisms attach themselves ¹ to Tyranids and slowly secrete powerful chemicals into the host's bloodstream during combat to boost it into a hyperactive bloodlust.²

Sources

• ¹:Codex: Tyranids (4th Edition), p.32
• ²: Codex: Tyranids (5th Edition), p.84