Several proteins in mice that might act as biomarkers for growth hormone have been uncovered by researchers at Ohio University.
Led by John Kopchick and Juan Ding, the research may prove to be the first step towards finding reliable way to detect recombinant human growth hormone (rhGH), which some athletes and teenagers use illegally to boost muscle and reduce fat.
The researches found four proteins that significantly decreased or increased in the blood after exposure to bovine growth hormone, which is similar to human growth hormone.
In the study, the researchers injected six 6-month-old male mice with growth hormone for seven days and examined blood samples from the mice and compared the results to six control animals. They also scanned hundreds of plasma proteins and found four - apoA1, transthyretin, clusterin and albumin - that showed a strong reaction to growth hormone.
"They're in the blood, but we don't know if they're coming from liver, fat, muscle or the kidneys," said Kopchick, Goll-Ohio Professor of Molecular Biology with Ohio University's Edison Biotechnology Institute and College of Osteopathic Medicine.
The researchers are hopeful that the proteins could be viable biomarkers for growth hormone activity in humans as well.
"In mice we can control the variables and the environment, but humans are genetically diverse and have different lifestyles that impact growth hormone. So the results may point to future study in humans, but may not necessarily apply to humans yet," said Ding, who also is studying how to identify protein biomarkers for human aging.
It is quite difficult to detect growth hormone as it has a serum half life of only 15 minutes. RhGH, an approved drug for individuals with growth hormone deficiency, also is identical to human growth hormone. The researchers said that the current method of detecting growth hormone, by analyzing levels of insulin-like growth factor (IGF-1), does not always prove accurate, as it is age and gender sensitive.
"If you have an 18-year-old Olympic athlete and a 38-year-old athlete, the IGF-1 values may look very different," said Kopchick.
He also said that because identification of rhGH misuse or abuse can make or break an athletic career, the current method has too many variables to depend on.
While it's not yet proved if these protein markers have the same age limitations, as the mice in the study live to only 2 years, but the markers may have longer half lives of several days, which would offer a wider testing window.
The study was presented at the Endocrine Society annual meeting in San Francisco.