Doping with growth hormone, a banned substance in sports, can be detected by changes to natural forms of growth hormone in the blood, and the test’s detection value does not decrease with simultaneous use of testosterone, according to a new study. The results will be presented Tuesday, June 16, at The Endocrine Society’s 90th Annual Meeting in San Francisco.

Surveys have shown that athletes who cheat at trying to improve sports performance commonly use growth hormone and testosterone together, said the study’s lead author, Anne Nelson, PhD. She is project manager of the Growth Hormone Doping Project of the Garvan Institute of Medical Research in Sydney, Australia. However, traditionally it has been difficult to detect growth hormone doping because the drug is indistinguishable from the growth hormone that the body naturally makes.

Their test measures different forms of growth hormone, called isoforms, which the pituitary gland releases into the body’s circulation. After someone takes growth hormone, there is a change in the relative amounts, or ratio, of the two main circulating isoforms: 20 and 22 kilodaltons (K). A large increase in the ratio of 22K to 20K is the basis for detection of growth hormone doping.

Nelson and her colleagues showed how the isoform ratio changed after giving growth hormone to young recreational athletes who volunteered for the study. In a carefully controlled study, they gave 95 adult volunteers daily injections of either growth hormone or an inactive placebo for 8 weeks. Some of the men received testosterone alone or in combination with growth hormone.

A rapid change occurred in the ratio of the 22K to 20K isoforms in blood samples after administration of growth hormone, according to Nelson. This change was greater in men than women, and use of testosterone did not affect it. However, the change in the ratio returned to pretreatment levels by 36 hours after treatment.

“This is a useful method for detection of growth hormone,” Nelson said. “Although the short time window of detection may limit the success rate of the test during competition, the isoform test is most likely to be effective when used in precompetition testing and in no-advance-notice out-of-competition testing.”

Information gained from the study will help the researchers fine-tune the robustness of the test, she added. Currently, the isoform ratios were greater in athletes who received growth hormone, compared with those who did not, about 55 percent of the time.

Growth hormone doping is thought to be widespread among athletes, according to Nelson. “It is important that a test for growth hormone doping is in place to deter the abuse of growth hormone,” she said.

The study was funded by the World Anti-Doping Agency and the Australian Government Anti-Doping Research Program. Novo Nordisk supplied the growth hormone for this study, and Organon provided testosterone.

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Founded in 1916, The Endocrine Society is the world's oldest, largest, and most active organization devoted to research on hormones and the clinical practice of endocrinology. Today, The Endocrine Society's membership consists of over 14,000 scientists, physicians, educators, nurses and students in more than 80 countries. Together, these members represent all basic, applied, and clinical interests in endocrinology. The Endocrine Society is based in Chevy Chase, Md. To learn more about the Society, and the field of endocrinology, visit our web site at www.endo-society.org.