Some have suggested that growth hormone is a wonder drug ( 16 ) that results in ripped muscle ( 17 ) and provides stamina-increasing properties ( 18 ) .
The use of human growth hormone to improve athletic performance has recently received worldwide attention .
This practice , often called sports doping , is banned by most professional sports leagues and associations , including the International Olympic Committee , Major League Baseball , and the National Football League ( 13 ) .
However , a wide range of athletes , including those from baseball ( 46 ) , cycling ( 7 , 8) , and track and field ( 5 , 9 ) , have been implicated in or have confessed to illicit growth hormone use .
The Mitchell report ( 10 ) recently identified 89 Major League Baseball players who allegedly used performance-enhancing drugs , and some of these players have subsequently admitted to using growth hormone ( 11 , 12 ) .
Part of the attraction of using growth hormone as a performance enhancer has been that its use is difficult to detect .
The World Anti-Doping Agency , whose formation stemmed from the widely publicized doping sc and al of the 1998 Tour de France ( 13 ) , first used a blood test to detect exogenous growth hormone during the 2004 Olympic Games in Athens .
Although growth hormone is reportedly used to enhance athletic performance and has been called the most anabolic substance known ( 15 ) , its efficacy for this purpose is not well established .
Exogenous growth hormone therapy in growth hormonedeficient adults ( that is , those with growth hormone deficiency due to hypothalamic or pituitary defects ) results in increased lean mass and decreased fat mass ( 19 ) , and comparable body composition changes are seen in healthy elderly adults who receive growth hormone ( 20 ) .
Some experts , however , have suggested that the strength-enhancing properties of growth hormone among healthy adults have been exaggerated ( 15 ) .
Serious side effects , including diabetes , hepatitis , and acute renal failure , may occur in athletes using high-dose growth hormone ( 21 ) .
Furthermore , the use of growth hormone for athletic enhancement is not approved by the U.S. Food and Drug Administration , and the distribution of growth hormone for this purpose is illegal in the United States ( 22 ) .
We performed a systematic review of r and omized , controlled trials to determine the effects of growth hormone therapy on athletic performance in healthy , physically fit , young adults .
Our primary aim was to evaluate the effects of growth hormone on body composition , strength , basal metabolism , and exercise capacity .
In addition , we sought to synthesize the evidence on adverse events associated with growth hormone in the healthy young and assess the quality of the published literature .
Changes in free rather than total insulin-like growth factor-I enhance insulin sensitivity and suppress endogenous peak growth hormone (GH) release following short-term low-dose GH administration in young healthy adults.
High-dose GH administration is commonly associated with impaired insulin sensitivity ( S(I ) ) in humans . Paradoxically we have shown that low-dose GH ( 1.7 microg/kg.d ) administration enhances beta-cell function in young healthy adults . In the present double-blind , placebo-controlled , cross-over study , we explored the physiological effects of this low GH dose on glucose metabolism in 12 young healthy adults ( seven males , 19 - 29 yr ) . At pretreatment and after each 14-d treatment block ,  overnight metabolic profiles were assessed followed by a hyperinsulinemic euglycemic clamp , whereas fasting blood sample s were collected weekly . In subjects treated with GH first ( group A , n = 6 ) , GH treatment increased total IGF-I ( P < 0.05 ) and IGF binding protein-3 ( P < 0.01 ) after 7 d , but these levels subsequently returned to pretreatment levels after 14 d. In contrast , free IGF-I increased ( P < 0.05 ) , and overnight GH pulse peak amplitude decreased ( P < 0.01 ) after 14 d. In subjects treated with placebo first ( group B , n = 6 ) , all biochemical parameters were unchanged after placebo treatment , whereas the changes in free and total IGF-I were similar to those of group A after GH treatment . Combined clamp data from both groups A and B ( n = 12 ) showed that 14-d GH treatment decreased overnight plasma insulin levels ( P < 0.02 ) and hepatic glucose appearance ( P < 0.05 ) and increased S(I ) ( P < 0.01 ) . Of note , the GH-induced changes in S(I ) positively correlated with the changes in free IGF-I ( r = 0.72 , P < 0.01 ) . In conclusion , low-dose GH administration enhanced S(I ) and suppressed endogenous peak GH release , and we hypothesize that these effects are the direct result of increased serum levels of free
Some have suggested that growth hormone is a wonder drug ( 16 ) that results in ripped muscle ( 17 ) and provides stamina-increasing properties ( 18 ) .
The use of human growth hormone to improve athletic performance has recently received worldwide attention .
This practice , often called sports doping , is banned by most professional sports leagues and associations , including the International Olympic Committee , Major League Baseball , and the National Football League ( 13 ) .
However , a wide range of athletes , including those from baseball ( 46 ) , cycling ( 7 , 8) , and track and field ( 5 , 9 ) , have been implicated in or have confessed to illicit growth hormone use .
The Mitchell report ( 10 ) recently identified 89 Major League Baseball players who allegedly used performance-enhancing drugs , and some of these players have subsequently admitted to using growth hormone ( 11 , 12 ) .
Part of the attraction of using growth hormone as a performance enhancer has been that its use is difficult to detect .
The World Anti-Doping Agency , whose formation stemmed from the widely publicized doping sc and al of the 1998 Tour de France ( 13 ) , first used a blood test to detect exogenous growth hormone during the 2004 Olympic Games in Athens .
Although growth hormone is reportedly used to enhance athletic performance and has been called the most anabolic substance known ( 15 ) , its efficacy for this purpose is not well established .
Exogenous growth hormone therapy in growth hormonedeficient adults ( that is , those with growth hormone deficiency due to hypothalamic or pituitary defects ) results in increased lean mass and decreased fat mass ( 19 ) , and comparable body composition changes are seen in healthy elderly adults who receive growth hormone ( 20 ) .
Some experts , however , have suggested that the strength-enhancing properties of growth hormone among healthy adults have been exaggerated ( 15 ) .
Serious side effects , including diabetes , hepatitis , and acute renal failure , may occur in athletes using high-dose growth hormone ( 21 ) .
Furthermore , the use of growth hormone for athletic enhancement is not approved by the U.S. Food and Drug Administration , and the distribution of growth hormone for this purpose is illegal in the United States ( 22 ) .
We performed a systematic review of r and omized , controlled trials to determine the effects of growth hormone therapy on athletic performance in healthy , physically fit , young adults .
Our primary aim was to evaluate the effects of growth hormone on body composition , strength , basal metabolism , and exercise capacity .
In addition , we sought to synthesize the evidence on adverse events associated with growth hormone in the healthy young and assess the quality of the published literature .