To put it bluntly, studies involving GH and healthy young men show that although circulating IGF-1 is elevated with GH therapy there is little or no change in muscle protein synthesis rates (1,2,3). Deysigg (1) looked at the effect of recombinant GH on strength, body composition and endocrine parameters in power athletes. Subjects received in a double-blind manner either GH treatment (0.09IU/kg/day) or placebo for a period of six weeks. To avoid confounding factors such as concurrent us of steroids, urine specimens were tested at regular intervals for these substances. Fat mass and lean body mass were derived from measurements of skinfolds at ten sites. GH, IGF-I and IGF-binding protein were in the normal range before therapy and increased significantly in the GH-treated group. Fasting insulin concentrations increased insignificantly and thyroxine levels decreased significantly in the GH-treated group. There was no effect of GH treatment on maximal strength or body composition.
Other studies have observed similar results. Yarasheski (2) conducted a 12 week study with sixteen men (21-34 yr) assigned randomly to a resistance training plus GH group (n = 7) or to a resistance training plus placebo group (n = 9). Both groups trained all major muscle groups in an identical fashion while receiving 40 µg GH/kg/day or placebo. Fat-free mass (FFM) and total body water increased in both groups but more in the GH recipients. Whole body protein synthesis rate increased more, and whole body protein balance was greater 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. The larger increase in FFM with GH treatment can simply be attributed to an increase in total body water. In this study as well as the previous one, resistance training supplemented with GH did not further enhance muscle growth or strength.
Later, Yarasheski performed a similar study but this time he used experienced weight lifters (3). Skeletal muscle protein synthesis and the whole body rate of protein breakdown were determined using labeled amino acids ([13C]leucine) in 7 young healthy experienced male weight lifters before and at the end of 14 days of subcutaneous GH administration (40 µg/kg/day). GH administration doubled fasting insulin-like growth factor-I levels, but did not increase the rate of muscle protein synthesis or reduce the rate of whole body protein breakdown. These findings confirm what others have found, namely that short-term GH treatment does not increase the rate of muscle protein synthesis or reduce the rate of whole body protein breakdown.
You may argue that in the real world, bodybuilders don’t use GH alone. It is generally combined with some form of anabolic steroid. Unfortunately I was unable to find a controlled study looking at the effectiveness of combining androgens and GH in healthy athletes for the purposes of building muscle. There is one study however that looked at the effects of combining both very high doses of androgens (up to 2.4 mg/kg/day) with or without concomitant GH use (4IU/day) (4). In all cases, using androgens with GH caused a significant decline in IGFBP3 levels. As you know, this dramatically decreases the half life of IGF-1 and thus the biological activity is attenuated. One other very enlightening finding of this study was that on a low calorie diet, it didn’t matter how much androgens or GH they were using, both IGF-1 and IGFBP-3 declined significantly. Clearly the effectiveness of any cycle using androgens with or without GH will be greatly diminished by lowering calories, and more importantly total protein. Still, the one question you may have, namely does high dose androgens make GH worth using, was not addresses by this study. The consensus generally is still no.
In HIV patients work is being done to determine if GH or androgens will prevent wasting. In these studies Deca Durablolin and other androgens have proven successful at preserving lean mass while GH has not proven to be effective (4). Concerning GH treatment in unhealthy populations, Michael Mooney, a well respected authority on HIV and muscle preservation, has challenged the claims made by at least one manufacturer of a GH product called Serostim. He wrote a letter to them challenging their claims that Serostim or any other brand of GH has true anabolic effects in this population.
"I underline that the only study of Serostim that included a critical evaluation of changes in muscle tissue to date showed no change and muscle using MRI (magnetic resonance imaging). All other studies so far have used Bioelectric Impedance Analysis, which measures lean body mass (LBM), but can not accurately measure changes in muscle. At the Third International Conference on Nutrition and HIV Infection at Cannes, France, April, 1999, Donald Kotler, M.D., of St. Lukes-Roosevelt Medical Center in New York reported the results of an interim analysis of a 6-month open-label trial of Serostim growth hormone. Dr. Kotler's data showed that 6 mg of Serostim per day did not promote a significant change in muscle tissue during the first 12 weeks in the 8 subjects for whom repeat MRI data were available. Several other studies with various HIV-negative populations have also shown no apparent improvement in muscle tissue."
So even in unhealthy populations, GH treatment does not increase muscle tissue growth. The final word on current methods of using subcutaneous GH and muscle growth is that it does not enhance muscle growth beyond what is accomplished by resistance exercise in healthy individuals
