Testicular size increased during pulsatile GnRH therapy, compared to previous HCG/ HMG therapy (P < 0.05).<h4>Conclusion</h4>For CHH patients with prior poor response to one year of HCG/ HMG therapy, switching to pulsatile GnRH therapy may induce spermatogenesis. The gene discussed is GNRH1; the disease is cartilage-hair hypoplasia.