**1. Introduction**

Prostaglandins (PGs), thromboxanes (TXs) and leukotrienes (LTs) collectively called eicosanoids, are cyclooxygenase (COX) and lipoxygenase (LOX) products. Prostanoids, PGs and TXs, are known effectors of a wide range of actions in most cells and tissues. They have been described to be involved in muscle contraction and relaxation, neurotransmitter release/unrelease, fever, sleep induction, apoptosis, cell proliferation and oncogenesis; but respecting endometriosis, what matters us mostly, is that they are central molecules involved in the reproductive system (Jabbour & Sales, 2004; Narumiya et al., 1999).
