After Brian Cushing tested positive for a banned substance, most folks wanted to know what it was. After he came out and said it was not steroids and he had a lie detector test to prove it, folks really wanted to know.
Well, here it is: Cushing had slightly elevated levels of human chorionic gonadotrophin (hCG), according to ESPN's Adam Schefter.
it is in seminal fluid and slightly elevated levels can be discovered in the event that a test occurs soon after ejaculation.
That's what Schefter (who has strangely been pro-Cushing through this story) says about it. And here's Wikipedia:
It's also commonly used during and after steroid cycles to maintain and restore testicular size as well as normal testosterone production.
You be the judge on why his levels of hCG were elevated.