A group of local tissue compounds with hormone-like effects. A large variety of prostaglandins exist with very different effects. Series 1 prostaglandins are strongly anti-inflammatory and reduce blood clotting. Series 2 prostaglandins have the exact opposite effect: they amplify and cause inflammation, increase pain perception and blood clotting. Series 3 prostaglandins, on the other hand, tend to have an anti-inflammatory effect.