This shows GH has a favorable influence on the immune system.....kind of. Although this study shows that GH increases NK cell activity, which is important against tumors and viral infections (and other intracellular infections), it doesn't tell you that when NK cell activity is increased (which is a part of Th1 immunity), that Th2 immunity is usually compromised to some degree, which means that one can be more susceptible to bacterial infections....or fungal infections.

The extent to which each "arm" of the immune system is altered also needs to be considered. This likely has no real dramatic practical's a good read though

Metabolism. 1990 Dec;39(12):1320-4. Related Articles, Links

Supplemental growth hormone increases the tumor cytotoxic activity of natural killer cells in healthy adults with normal growth hormone secretion.

Crist DM, Kraner JC.

Department of Medicine, University of New Mexico School of Medicine, Albuquerque 87131.

Using double-blind, placebo-controlled procedures, the effects of methionyl-human growth hormone (met-hGH) on the tumor cytotoxic activity of natural killer (NK) cells were studied in seven healthy adults using a repeated measures experiment. Subjects were assigned at random to either a placebo (bacteriostatic water) treatment condition or a met-hGH (16.0 mg/wk of Protropin) treatment condition, then crossed-over to the alternative treatment. Treatments were delivered on alternate days (3 d/wk) for 6 weeks. Without bias from the met-hGH treatment, there was no evidence for GH hyposecretion as measured by the peak circulating GH response to exercise stimulation (14.1 +/- 3.1 ng/mL) or insulin -like growth factor (IGF-I) levels (0.82 +/- 0.09 U/mL). When compared with placebo, met-hGH induced a significant overall increase in the percent specific lysis (%SL) of K562 tumor target cells (placebo 22.2 +/- 1.7 v met-hGH 28.5 +/- 2.1 %SL; P = .008). NK activity was increased within the first week of treatment and this level was maintained throughout the remaining period of supplementation. There was a trend (P = .057) for the met-hGH-induced percent change in NK activity (NK%) to be inversely related to placebo IGF-I levels (r = -.761), while there were significant positive correlations between NK% and the met-hGH-induced percent changes in IGF-I (r = .727; P = .035), the fat-free mass (FFM)/fat mass (FM) ratio derived by hydrodensitometry (r = .792; P = .012), and the endogenous GH response to exercise (r = .469; P = .034).(ABSTRACT TRUNCATED AT 250 WORDS)