In pharmaceuticals pyrogens and endotoxins are related to bacterial endotoxin testing. These two terms used interchangeably sometimes but the thing is that both have different meanings. So what is the difference?
See biology is very easy if you break the terms. now see
Pyrogens = Pyro + Gen
That means heat generator(one who can gererate warmth) now if you are concerned with human body the oraganisms or factors that cause to raise the body temperature is known to be pyrogens.
Endotoxin = Endo + Toxin
That means that the toxin which produces its effects inside. with respect to human body the toxic substances or organism that produces toxin inside the cell or show their effect when inside the cell.
Pyrogens are the substances which cause rise in body temperature and induces fever. Pyrogen can be external or internal like any forgein particle when entered in body can act as pyrogen or body’s internal molecules can act as pyrogen.
So if we look the term pyrogen, it has a wide range which includes forgein particles, internal molecules etc. But endotoxins are released by the cell wall of the gram negative bacteria after cell death. These are basically lipopolysaccharides (LPS) in nature. Endotoxins when gets inside the body also cause rise in temperature and induce fever but endotoxin are one of the category of pyrogens.
So all endotoxins are pyrogens but all pyrogens are not endotoxins.