Background: Growth hormone (GH) plays a role in thymic function, and recombinant GH stimulates thymopoiesis in HIV-infected individuals.

Methods:  We performed immunological analyses in 26 antiretroviral-treated children matched for age, pubertal status, clinical parameters, and antiretroviral exposure, who did or did not show an impaired response to GH-release stimulation tests with arginine + GH releasing hormone.

Results: The following parameters were significantly reduced in GH-deficient children after >4 years of therapy: CD4 counts (p= 0.02) and percentages (p = 0.03), CD4 as percentage of normal for age (p = = 0.003), serum IL-7 (p =  0.02), thymic volume (p = 0.01). Naive CD4 (4+62+RA+ and 4+CCR7+RA+) and CD8 (8+CCR7+RA+) lymphocytes were lower in GH-deficient children (p =  0.003; p = 0.007; andp =  0.02). Post-thymic pathways were also impaired in GH-deficient children. Thus, CD4⁺ central memory cells (4+CCR7+RA-) were reduced (p =  0.006), whereas CD4⁺ effector memory lymphocytes (4+CCR7-RA-) (p =  0.002) and late effector CD8⁺ lymphocytes (8+CCR7-RA+ and 8+27-28-)(p =  0.009 and p =  0.002) were increased in these children.

Conclusions: GH plays a pivotal role in thymic and post-thymic pathways, and defective GH production is associated with incomplete immunoreconstitution. More aggressive antiviral regimens and the use of immunomodulants (including GH) should be considered in patients with defective GH production.

Keywords: growth hormon; immunology; antivirla therapy