Antagonists and Agonists.. or "I coulda been a contendah!"

OK... this is silly, I'll say it right up front.  There.

I've been mucking about reading about hormones, agonists, antagonists, and trying to make some sense of what it is I signed up for (willingly, I should emphasize... I just didn't appreciate the complexity of the interactions going on here).  And I was casting about for a visual image for an agonist, because I felt like I was leaving the poor agonist out of the picture.  So ...brace yourself.  It's Marlon Brando in "On the Waterfront" asserting that he coulda been a contendah.

Where did that come from?  Good question! The Greek background of the word "agonist", which is this
"The word "agonist" comes from the Late Latin agnista, contender, from the Greek agnists, contestant, from agn, contest. An agonist is a chemical contestant or contender."

OK... that wasn't as funny as I thought.  Interesting words, these... and a bit confusing as well.  I mean, an antagonist is the bad guy in a story, right? And he or she plays against the protagonist.  Except not here.  It's another example of medical (terminology) humor. HA!  It is to laugh!  Only it would help for the medical terminology to be somewhat less opaque to the patient side of the equation.