Lowinson and Ruiz's Substance Abuse: A Comprehensive Textbook edited by Pedro Ruiz, Eric C. Strain (discussion of HGH, use in sports, anti-aging clinics, prior testing by NFL, etc.)

https://books.google.com/books?id=w4ZUJAdleTsC&pg=PA359&dq=anti-aging+clinics&hl=en&sa=X&ved=0ahUKEwjNhrS0iP_JAhVL5mMKHcO4BAQQ6AEIQjAD#v=onepage&q=anti-aging%20clinics&f=false