That honor went to Kurt Marnul.
Not Kurt Marnul, at least not GH. Steroids yes, but that is it.
BTW Non human GH does not work in humans. In the early 80's moneky GH was supposedly availible on the black market, but it turned out to be bullshit.
Marnal trained with Arnold in Thal Austria, when Arnold was between 15 and 18. At age 18 Arnold went in the Austrian Army, then he went to manage a gym in Germany, where he met Franco. In 1969, at the age of 22 Arnold came to America-so Marnal had been out of the picture for at least 5 years before stepping foot in America.