Problem We aimed to investigate the effect of gonadotropin-releasing hormone ( Gn RH) analogues on T-cell immunity. Method of study TNF-α+-, INF-ɣ+-, IL-10+-, and IL-17+-expressing T cells in peripheral blood mononuclear cells ( PBMCs) were treated with various concentrations (0.1, 1, 5, and 10 μ m) of Gn RH agonist (buserelin acetate) and antagonist (cetrorelix acetate) for 4 hours in vitro and they were analyzed with flow cytometry. Results TNF-α+/IL-10+ T helper ( TH) cell ratios were increased in PBMCs treated with 1, 5, and 10 μ m Gn RH agonist when compared to controls ( P=.006, P=.014 and P=.030, respectively). IFN-ɣ+/ IL-10+ TH cell ratios were significantly increased with 0.1, 1, 5, and 10 μ m Gn RH agonist as compared with controls ( P=.046, P=.004, P=.013, and P=.011, respectively). TNF-α+ TH cell levels, and IFN-γ+/IL-10+ TH cell ratios were significantly different ( P<.001 and P<.004, respectively) between Gn RH agonist- and antagonist-treated cells. Conclusion Gn RH analogues induce pro-inflammatory TH1 shift in T-cell immunity, in vitro. Gn RH treatment during assisted reproductive technology cycle might explain a possible cause of inflammatory flare in women with inflammatory conditions. [ABSTRACT FROM AUTHOR]