J Endocrinol Invest. 1999;22(5 Suppl):106-9. Related Articles, Links
Growth hormone and body composition in athletes.
Frisch H.
Department of Pediatrics, University of Vienna, Austria.
herwig.frisch@akh-wien.ac.at
The anabolic properties of growth hormone (GH) have been investigated extensively. The effects of GH on normal, hypertrophied and atrophied muscles have been studied previously in animal experiments that demonstrated an increase in muscle weight and size, but no comparable increase in performance or tension. In adults with GH deficiency, the changes in body composition can be corrected by GH treatment; lean body mass and strength increase within a few months. In children with GH deficiency, Turner's syndrome or intrauterine growth retardation, an increase in muscle tissue is seen after treatment with GH. In acromegalics with long-standing GH hypersecretion, the muscle volume is increased, but muscle strength and performance are not improved. These observations gave rise to the interest shown by healthy subjects and athletes in using GH to increase their muscle mass and strength.
The improvements in muscle strength obtained by resistance exercise training in healthy older men or young men were not enhanced by additional administration of GH. The larger increases in fat-free mass observed in the GH-treated groups were obviously not due to accretion of contractile protein, but rather to fluid retention or accumulation of connective tissue. In experienced weightlifters, the incorporation of amino acids into skeletal muscle protein was not increased and the rate of whole body protein breakdown was not decreased by short-term administration of GH. The results of a study in power athletes confirm the results of these investigations. The study used GH treatment in power athletes compared with a placebo-control group, and the results indicated no increase in maximal strength during concentric contraction of the biceps and quadriceps muscles, although levels of insulin-like growth factor-I were doubled. In highly trained power athletes with low fat mass and high lean body mass, no additional effect of GH treatment on strength is to be expected.
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Exerc Sport Sci Rev. 1994;22:285-312. Related Articles, Links
Growth hormone effects on metabolism, body composition, muscle mass, and strength.
Yarasheski KE.
Metabolism Division, Washington University School of Medicine, St. Louis, Missouri.
It is clear that the anthropometric ramifications, especially with respect to muscle mass, of the metabolic actions of GH and IGF-I treatment in intact and GH-deficient adults require further study. At present, it appears that daily GH or IGF-I treatment modestly increases nitrogen retention in most normal adults, probably by separate but permissive mechanisms, but only for a short period of time (approximately 1 month). During prolonged GH administration, resistance to the anabolic actions of GH seems to occur, and optimizing the anabolic effects of GH or IGF-I treatment will require a better understanding of the interactions among GH, GHBP, IGF-I production, IGFBPs, the GH dose regimen, and other unidentified regulatory factors.
On the basis of the similar increases in muscle protein synthesis, muscle cross-sectional area, and muscle strength observed in placebo and GH-treated exercising young adults, it is doubtful that the nitrogen retention associated with daily GH treatment results in an increase in contractile protein, improved muscle function, strength and athletic performance. Even in catabolic or GH-deficient populations, GH treatment provides only modest increments in nitrogen retention, muscle size, strength, and exercise capacity. Further, the side effects of GH treatment (water retention, carpal tunnel compression, insulin resistance) would be a detriment, rather than an aid, to athletic performance. In addition, whether prolonged (> 6 months) GH treatment alone or in combination with other agents used by athletes (e.g., anabolic steroids, beta-agonists) is associated with other adverse side effects (e.g., cancer, diabetes) has not been evaluated. Therefore, health professionals should continue to discourage the use of GH by exercise enthusiasts.
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Am J Physiol. 1992 Mar;262(3 Pt 1):E261-7. Related Articles, Links
Effect of growth hormone and resistance exercise on muscle growth in young men.
Yarasheski KE, Campbell JA, Smith K, Rennie MJ, Holloszy JO, Bier DM.
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
The purpose of this study was to determine whether growth hormone (GH) administration enhances the muscle anabolism associated with heavy-resistance exercise. Sixteen men (21-34 yr) were assigned randomly to a resistance training plus GH group (n = 7) or to a resistance training plus placebo group (n = 9). For 12 wk, both groups trained all major muscle groups in an identical fashion while receiving 40 micrograms recombinant human GH.kg-1.day-1 or placebo. Fat-free mass (FFM) and total body water increased (P less than 0.05) in both groups but more (P less than 0.01) in the GH recipients. Whole body protein synthesis rate increased more (P less than 0.03), and whole body protein balance was greater (P = 0.01) in the GH-treated group, but quadriceps muscle protein synthesis rate, torso and limb circumferences, and muscle strength did not increase more in the GH-treated group. In the young men studied, resistance exercise with or without GH resulted in similar increments in muscle size, strength, and muscle protein synthesis, indicating that 1) the larger increase in FFM with GH treatment was probably due to an increase in lean tissue other than skeletal muscle and 2) resistance training supplemented with GH did not further enhance muscle anabolism and function.
