pros·ta·glan·din 
(prŏs′tə-glăndĭn)
(prŏs′tə-glăndĭn)n.
Any of a group of potent hormonelike substances that are produced in various mammalian tissues, are derived from arachidonic acid, and mediate a wide range of physiological functions, such as control of blood pressure, contraction of smooth muscle, and modulation of inflammation.
[PROSTA(TE) GLAND (from the mistaken belief that the first prostaglandin discovered was secreted by the prostate) + -IN.]