Why are prostaglandins sometimes called tissue hormones?

Prostaglandins are clever chemical messengers that exist in every cell of the body — and in all sorts of living creatures throughout the animal kingdom. They act like hormones, which are substances that coordinate different biological functions. Most hormones move from glands to the bloodstream to target organs to do their jobs. Prostaglandins, however, stay put within the cells to serve as catalysts for stuff like cell division, clotting, reproductive processes, and lots more.

These biochemicals have been causing a stir since their discovery in 1936. They're mysterious, complicated, and critical to life. Research into these substances has produced fascinating data on how they're made and what they do. For example, aspirin was created to reduce pain by stopping cells from making prostaglandin.

Here's how it works: You bump into the edge of your desk (ouch!). Because your leg now has tissue damage, white blood cells rush to the site of the injury to try to minimize the harm done. Prostaglandins are produced as a result. Too much prostaglandin means pain, swelling, and even fever. Through a series of chemical reactions in cells, aspirin turns down the volume on the pain messages being sent to the brain — and your body can get back to the business of healing.