Harvard scientists say illicit human growth hormone (HGH), which is widely used among young American male weightlifters, is often linked to polysubstance abuse involving both performance-enhancing and street drugs.

Human growth hormone of concern is a protein that is manufactured to be nearly identical to the main form of the naturally occurring human growth hormone.

This hormone can stimulate tissue growth, linear growth (height), protein, carbohydrate, lipid, and mineral metabolism.

The researchers from Harvard Medical School accessed 231 male weightlifters ages 18 to 40 and their reports of drug use, found 27 of the subjects reported use of HGH and/or insulin-like growth factor-I.

The 27 participants had also used anabolic androgenic steroids (AAS) and among them, 15 also had opioids, cocaine, and/or ecstasy.

The results show that use of illegal HGH is common, and often is linked to the use of street drugs.

Until December of last year, the U.S. Food and Drug Administration believed the benefits of recombinant growth hormone continue to outweigh its potential risks.

Growth hormone and insulin-like growth factor-I promote cancer growth, previous studies found.

Stephen Lau and editing by Aimee Keenan-Greene