Assessment of immune function after short-term administration of recombinant human growth hormone in healthy young males

Abstract

It is reported that in both elite and recreational athletes Growth Hormone (GH) is the most commonly used drug aimed at improving sport performance. Aim: The purpose of the present study was to evaluate the immunomodulatory effects of short-term administration of recombinant human GH (rhGH) in healthy young males. NK cell number, activity and phenotype, T cell number, cytokine production of IL-2, IL-4, IL-6, IL-10, TNF-α and IFN-γ and CD4 + /CD8 + ratio with particular attention to the possible correlation to IGF-I production were investigated. Methodology: 30 healthy young males (27 ± 9 yrs) were randomly assigned to either placebo (n = 15) or drug (rhGH) 1mg/day groups (n = 15) with daily injection for seven days. IGF-I serum concentration and flow cytometry data were generated at baseline (day 0) and days 8, 15, 22 and 29 post injection. Data was analysed using a General Linear Model with repeated measures with a Bonferroni correction factor and significance set at p≤0.05. Results: The T cell cytokine secretion profile indicated a Th1 -Th2 shift. Interestingly, a significant difference (p≤0.05) of IL-10 mean fluorescence is noted from day 15 (P= 35.14; ± 19.93, rhGH = 26.63; ± 16.39) to day 22 (P= 61.32; ± 20.41, rhGH= 74.99; ± 46.91) and to day 29 (P= 101.98; ± 67.25, rhGH= 107.74; ± 122.58). Serum IGF-I concentration (ng/mL) increased significantly (p≤0.01) on day 8 (0.48 ± 0.78) after injections compared to baseline (0.31 ± 0.07) as well at day 15 (0.33 ± 0.06), 22 (0.29 ± 0.05) and 29 (0.29 ± 0.06). In conclusion, the cytokine secretion spectrum is affected by short-term rhGH administration in healthy young males being suggested to have induced CD4 + T lymphocytes production of IL-10.

Relationship between Growth Hormone and Cytokines in Short Children Undergoing Growth Hormone Stimulation Testing

“…Our findings are similar to those demonstrated by Michalacous et al in which GH did not correlate with TNF α in GH deficient children or in short stature children as a group [8]. Ramos et al also failed to identify a relationship between acute GH administration and cytokine production in a population of healthy young men [7].…”

“…To the contrary, other studies conducted in healthy young males as well as post-surgical patients demonstrate no effect of short term GH administration on cytokine secretion [7] [10]. Micahelous et al also revealed no correlation between TNF α and GH levels in GH deficient or idiopathic short stature patients [8].…”

“…GH has been found to stimulate TNF α release in adults and children [5] [6]; however, there has been inconsistent documentation within the literature [7]- [9]. Research in hypophysectomized rats demonstrate a significant reduction in in vitro macrophage production of TNF α after stimulation with lipopolysaccharide [3].…”

Insulin‐like growth factor‐1 and insulin‐like growth factor binding protein‐3: impact on early haematopoietic reconstitution following allogeneic haematopoietic stem cell transplantation

“…Previous studies have shown both positive and negative results regarding the effects of GH treatment on the haematopoietic system with findings of both increased haematopoiesis 44,45 and enhanced NK cell activity, 16,38,39 as well as unaffected blood cell counts 36,46,47 . As the negative findings are conducted in studies involving healthy subjects, it seems likely that patients with immune depletion have a more pronounced effect of supplementary GH and IGF‐1, while immune function in healthy individuals is largely independent of these hormones 47 …”