Recombinant human growth hormone—Effects on cytokine production in healthy young males

Abstract

Introduction: Growth hormone (GH) has being used for different clinical purposes resulting in improvement of immunological function of patients with impaired immune system. However, there is paucity in the literature examining the potential effects of recombinant human GH (rhGH) on lymphocytes and cytokine production of healthy populations. The aim of the present study was to investigate the effect of short term (7 days) administration of exogenous rhGH on T lymphocytes (CD4; CD8) and cytokine production—IL-2, IL-4, IL-6, IL-10, tumour necrosis factor (TNF)-α and interferon (IFN)-γ on human peripheral blood mononuclear cells (PBMC), and their relation with IGF-I levels in healthy young males. Methodology: 30 young males (25.7 yrs ± 7.80 SD) participated in a 29 days study where either 0.9% sodium chloride or 1 mg of rhGH was administered from day 1 to day 7. The participants were randomly assigned into either placebo (P; n = 15; 26.1 ± 6.6 yrs)) or rhGH 1 mg/day (n = 15; 24.5 ± 6.5 yrs). Baseline (day 0) and post injections samples (days 8, 15, 22 and 29) were analysed for IGF-I, T cells numbers and cytokine production at PBMC. General Linear Model with repeated measures was applied and Bonferroni's correction factor was utilized with p ≤ 0.05 denoting statistical significance. Results: T cells numbers and CD4/CD8 ratio presented no difference however Th2 cytokines increased indicating a shift from Th1 to Th2 from day 15 to days 22 and 29. Specifically, there was a significant difference between groups for IL-10 (Mean Fluorescence Intensity, MFI) at day 15 (P = 35.14; ±19.93 SD, rhGH = 26.63; ±16.39 SD), day 22 (P = 61.32; ±20.41 SD, rhGH = 74.99; ±46.91 SD), day 29 (P = 101.98; ±67.25 SD, rhGH = 107.74; ±122.58 SD). Plasma IGF-I (ng/mL) increased significantly on day 8 (0.48 ± 0.78 SD) after injections compared to baseline (0.31 ± 0.07 SD), day 15 (0.33 ± 0.06 SD), 22 (0.29 ± 0.05 SD) and 29 (0.29 ± 0.06 SD). Conclusion: Although the lymphocyte numbers were not significantly different from baseline to day 29 between groups, cytokine production showed a significant increase over the post administration. It is conclusive that cytokine release can be affected by short-term rhGH administration in healthy young males suggesting that rhGH may act on CD4+T lymphocytes to increase IL-10 production.