Objective: To investigate the impact of growth hormone (GH) therapy in adults with childhood-onset GH deficiency on immune system.
Methods: Ten young GH deficient adults (7 males, age 19-28 years) were treated with recombinant human growth hormone for 6 months. The starting dose was 0.5 IU/m2/day (2 weeks), then it was doubled to 1.0 IU/m2/day. In 5/10 patients, the dose was further increased to 1.5 IU/m2/day at 4 weeks of therapy. Immunological studies were performed before treatment and after 6 weeks, 3 months and 6 months and included humoral (IgG, IgA, IgM, C3, C4 and immune complexes) and cellular parameters (total lymphocyte count and counts of CD3+, CD4+, CD8+ and CD19+ lymphocytes, the CD4+/CD8+ ratio and percentage of CD16+56+ and CD3+DR+).
Results: The cellular responses to GH therapy were subtle, but detectable, with the trend to the higher CD4+ and lower CD8+ lymphocytes and maximal changes at 6 months of therapy. They were reflected in CD4/CD8 ratio, which increased from 1.15 +/- 0.10 (mean +/- S.E.; baseline) to 1.37 +/- 0.11 (6 weeks; P < 0.05), 1.24 +/- 0.10 (3 months; n.s.) and to 1.59 +/- 0.20 (6 months; P < 0.05). The response in humoral immunity was characterized by a rapid decrease of circulating immunoglobulins (IgA: 1.40 +/- 0.25 g/l [mean+/-S.E.], baseline; 1.12 +/- 0.19, at 6 weeks; P < 0.05) and C4 (0.25 +/- 0.02 g/l, baseline; 0.19 +/- 0.01, at 6 weeks; P < 0.05) and a tendency to an increase in circulating immune complexes (29.1 +/- 8.1, baseline; 40.3 +/- 7.2, at 6 weeks; n.s.). These observations suggest a temporary immune complex formation after the onset of GH treatment which might play a partial role in developing oedema as a side effect of GH treatment, besides the known effect of GH on water retention.
Conclusions: GH therapy in GH deficient young adults has a measurable effect on the increase of CD4/CD8 ratio and on the formation of immune complexes.