Recombinant Growth Hormone Administration in Athletics
The quest for improved human performance has been a never-ending search that has driven athletes since the genesis of games and sport. It is rational to hypothesize that athletes have experimented with just about everything known that can be consumed to improve their athletic performance. As the financial rewards and prestige for elite athletic performance increase, the search for ergogenic aids that improve physical ability is likely to intensify. The cross-section of sports involved in the use of performance enhancement substances is rapidly increasing. This may be largely due to the easy accessibility to a diverse array of pharmacological substances, which has also broaden the range of physiological systems that can be manipulated for increased performance. Recombinant Human Growth Hormone (rhGH) is currently hailed as the fountain of youth and has been embraced by athletes for turning their bodies into younger, sleeker, and stronger performance machines. Growth hormone (GH) has been promoted in the athletic community as an ergogenic aid that can increase muscle hypertrophy and strength, increase local muscle endurance, reduce body fat, and has also been credited with the capacity to induce hyperplasia (the division of muscle cells).
GH has also become appealing to athletes because it is one of the hardly detectable drugs. The International Olympic Committee outlaws growth hormone, however the World Anti-Doping Agency has admitted that it is not likely to introduce a new and effective test before the 2004 Olympic games in Athens, Greece (Fordyce, 2003). Due to the notion of GH’s efficacious ergogenic effect and hardly detectable nature, the proliferation of use is generally expected, and even accepted by some within the athletic community. The mechanisms of GH on metabolism and tissue growth are extremely complex; hence the use of exogenous GH supplementation is not fully understood. Research to date has yielded conflicting data concerning its benefits in performance enhancement. The intent of this review is to summarize the current research findings on the use and physiological adaptations of exogenous GH supplementation, as well as to examine the efficacy on performance and possible side effects.
Growth Hormone-Its Use, Effects, and Function
Growth hormone is secreted by the anterior pituitary gland and exerts many effects on the human body. The effected target tissues of GH may include bone, immune cells, skeletal muscle, fat cells, and liver cells. An important function of GH is to stimulate growth in children who suffering with GH deficiency. The development of a biosynthetic replication of human growth hormone took place in 1985 (History Of Growth Hormone, 2003). Synthetic Recombinant GH (rhGH) is originally used to help children with insufficient hormone levels for reaching their full height. However, it is an accessible item on the black market today. It is genuinely accepted that bodybuilders were the first amongst athletes to use rhGH to increase lypolysis. Since then, athletes who involve in track and field, weightlifting, and wrestling which require greater degrees of strength, power, and speed have pervasively used rhGH.
The main physiological roles of GH include increasing amino acid transport across cell membranes resulting in increased protein synthesis. GH decreases glycogen synthesis and glucose utilization; as such this results in increases in both the utilization of fatty acids and lipolysis (fat breakdown). So the availability of glucose and amino acids maintains at a high level, as well as collagen synthesis, which stimulates cartilage growth. GH also affects the retention level of nitrogen, sodium, potassium, and phosphorus and the immune cell function (Baechle & Earle, 2000). Apparently, GH has an anabolic effect on many target cells throughout the human body. This is appealing to an athlete who is interested accelerating the recovery process and promoting tissue growth beyond normal human physiological capacity. Thus, it is assumes that rhGH could elicit greater muscle strength and power via increasing protein synthesis, and reduce an athlete’s bodyfat through accelerated lypolysis, as well as foster collagen synthesis to stimulate cartilage growth, which strengthens and increases the resiliency of connective tissue.
The Effects of Recombinant Growth Hormone
It is importance to understand that the vast majority of research on rhGH administration is related to the treatment of individuals suffering from growth hormone deficiency, or from severe obesity. Research on rhGH administration has not been without methodological problems. The existing studies that examined the effects of rhGH for a variety of therapeutic treatments usually do not propose operational definition of optimum dosages (Hennessey et al, 2001; Palkhivala, 2003; Rudman et al, 1990). The duration of treatments in those studies also have varied significantly. In general, there is much less data available on the effects of rhGH as an ergogenic aid for enhancing athletic performance.
The studies on administration of rhGH in healthy adults and young athletes have yielded mixed results in terms of changes in strength and body composition. Positive results were found that rhGH might be beneficial to athletes and bodybuilders for weight loss and maintaining lean body mass (Deus, 2004). One study found reduction in fat weight and increases in fat-free weight with rhGH administration in 8 well-trained men on a resistance-training program (Foss & Keteyian, 1998). Crist and colleagues (1988) also supported the use of rhGH (30 -50 mcg/kg, 3 days per week for 6 weeks) can promote fat loss. The reduction of body fat and preservation of lean tissue can be advantageous to athletes requiring speed, power, jumping ability, and agility (Baechle & Earle, 2000). Furthermore, the study of Yarasheski (1993) also showed that rhGH appears to contribute to increased muscle hypertrophy and strength.
Although the promotion of lypolysis with rhGH supplementation has been widely accepted in the athletic community, Deyssig and colleagues’ study (1993) did not favor this conclusion. In addition, they proposed there was no significant increase in muscle strength after rhGH administration, either. The study of Henrik et al. (2002) is well cited in the literature showing that rhGH administration is not an effective means for increasing muscle strength or mass-either alone or combined with resistance training-in elderly men. A review study from Winnipeg concluded that there is no controlled data showing rhGH helps make athletes stronger (Dean, 2002). Rennie (2003) indicated that growth hormone does indeed have powerful effects on fat and carbohydrate metabolism; however, there is no proof that net protein retention is promoted in adults, except possibly of connective tissue.
Apparently, there is a paucity of data on the effects rhGH on cardiovascular or muscular endurance. Nevertheless, the results seem to be more consistent than the investigations on lypolysis, strength, and hypertrophy. Cardiovascular and muscular endurance adaptations are not often cited in the literature. Studies have found that healthy endurance athletes were unable to complete accustomed cycling tasks after administration of rhGH. Researchers hypothesized that an increase in plasma lactate could result from the inhibition of the enzyme pyruvate dehydrogenase (PDH) by high levels of fatty acids released during rhGH-stimulated lipolysis (Deus, 2004). Woodhouse, Asa, Thomas, and Ezzat (1999) examined the aerobic performance of GH-deficient adults who were engaging in the rhGH treatment. The participants’ maximal oxygen uptake (VO2 max) was measured at baseline, and after four months of treatment. The study found no significant increase in VO2 max.
Performance Degradation and Side Effects
Athletes may spend exorbitant amounts of money on rhGH administration and actually experienced performance degradation. Rennie (2003) concluded that rhGH administration to trained athletes might impair their performance. If rhGH does stimulate muscle size at all, it results in hypertrophy with less force production from exercise-induced hypertrophy. An increase in mass without a proportional increase in strength may reduce an athlete’s production of speed, power, agility, and endurance. The edema associated with rhGH administration could also impair athletic performance. Many users may experience the arthralgia (joint pain).
The possibility of degradation in athletic performance with rhGH administration is closely related with a variety of secondary side-effects. Insulin resistance is a common side effect of rhGH use and would be expected to reduce glucose availability. The administration also results in the impairment of muscle and liver glycogen storage. Rennie (2003) further suggested that fatty academia resulting from rhGH-induced lypolysis could promote cardiac arrhythmia during intense exercise. In addition, rhGH administration in humans has been shown to induce a shift in muscle fiber type from type IIa to IIx. The latter has been characterized as the “default” fiber type since the proportion of 2x fibers to type I and type IIa is relatively high in “couch potatoes” compared to strength and power athletes. If rhGH administration induces a shift in fiber type away from the trained state, this could have negative implications for strength and power athletes. (Deus, 2004)
Taking rhGH over a period of time can also cause acromegaly. This occurs because the end of the long bone (epiphyses) in the mature skeleton is fused. It is needless to say the cosmetic implications are not visually pleasing. Other side-effects include elevated blood pressure and an increased risk of cardiovascular disease.
Summary and Conclusions
Until cost-effective and accurate testing methods are developed for detection, some athletes will absorb the exorbitant cost, and risk ominous side effect as long as they are convinced administration will get them leaner, stronger, and faster. A concerted effort must be made to develop effective testing methods so rhGH administration can be extricated as an ergogenic aid in sports within the United States, and internationally.
Despite the existence of the negative connotations in strength or muscle mass increase resulting from rhGH administration, the majority of research data have not examined the rhGH administration exclusively for promoting athletic performance. At this moment, there is no robust, credible study demonstrating clear effects of either medium to long term rhGH administration, alone or in combination with a variety of training protocols, on muscle protein synthesis, mass, strength, or body composition. Researchers have also noted that studies on the elite athletes probably would not able to discover any statistical significance in their performance improvement from rhGH use. However, a slight 1-2% improvement could make all the difference in the world to an elite weightlifter, sprinter, swimmer, or cyclists and trigger them to use rhGH.
The research methodologies used to study the effects of rhGH will affect its outcome. The most of the studies related to the therapeutic treatment for rhGH do not examine the efficacy on aerobic capacity and muscular endurance. Ongoing research on the administration of rhGH toward this direction is warranted. Valid data from performance-related studies must be afforded to the international sport community for preserving the ethical integrity of sports, and for protecting the health of all athletes participating.
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