Horse hormones put athletes at risk

A Sydney endocrinologist says athletes who inject themselves with the illegal drug Equigen put their lives and careers at risk for no benefit.

Professor Ken Ho, head of the pituitary research unit at the Garvan Institute, and head of endocrinology at St Vincent’s Hospital, said Equigen – bioengineered equine growth hormone - simply doesn’t work in humans.

Research has shown that the molecular structure of equine growth hormone (eGH) differs so much from that of human growth hormone (hGH) its human equivalent that it cannot activate hGH receptors.

HGH, produced by the pituitary gland in the brain, acts as a signalling molecule, binding to receptors on liver cells and switching on production of the “real” growth hormone, insulin-like growth factor 1 (IGF-1).

IGF-1 builds and strengthens muscles. With the advent of a new test for illegal use of IGF-1, some athletes resorted to using its “releaser”, hGH.

Now, with drug-testing evaluating tests for hGH, some athletes – like Australian world junior cycling champion Mark French, banned for life from Olympic representation – appear to be experimenting with growth hormones from other mammal species.

Bioengineered porcine, bovine and equine growth hormones are widely used in the livestock industries to boost productivity, but no tests are available to detect their illegal use by athletes.

An expert on drug-testing in sport, who declined to identified, told Australian Biotechnology News this week that drug-testing agencies assumed that athletes wouldn’t use them because they don’t work in humans.

Ho, whose Garvan research group is currently evaluating a test to detect hGH, said athletes who experimented with non-primate growth hormones were doing themselves no good, and exposing themselves to great harm.

When a drug like Equigen is injected into the bloodstream, it rapidly elicits an antibody response because the human immune system regards it as alien.

Depending on the genotype of the particular athlete, the resulting antibody-antigen complexes could cause problems ranging from anaphylactic shock on a follow-up injection, to mild arthritis and life-threatening kidney disease.

Ho said there was also a risk, despite the differences between eGH and hGH, that the immune system would attack domains common to both molecules, and then attack endogenous human growth hormone.

“It can’t be ruled out – these sorts of immune problems are known for many different types of protein,” Ho said.

Ho’s Garvan research group is involved in a $1.2 million international research project, sponsored by the World Anti-Doping Agency, to develop a reliable test to catch athletes using recombinant human growth hormone illegally.