An Associated Press investigation shows that a federal crackdown on illicit foreign supplies of human growth hormone has failed to stop rampant misuse, and instead has driven record sales of the drug by some of the world's biggest pharmaceutical companies.

The crackdown, which began in 2006, reduced the illegal flow of unregulated supplies from China, India and Mexico. But since then, Big Pharma has been satisfying the steady desires of U.S. users and abusers, including many who take the drug in the false hope of delaying aging.

An AP analysis of pharmaceutical company data shows that from 2005 to 2011, inflation-adjusted sales of HGH were up 69 percent. During the same period, sales of the average prescription drug rose 12 percent.

Under U.S. law, HGH can only be dispensed for very rare conditions.