Effect of treatment with cyproterone acetate on uterine bleeding at the beginning of GnRH analogue therapy in girls with idiopathic central precocious puberty

Abstract Background: The flare-up effect of GnRH analogues may cause transient uterine bleeding in girls affected with idiopathic central precocious puberty (ICPP). Aims: To assess the incidence of endometrial bleeding and verify whether pretreatment with cyproterone acetate could counteract it. Methods: Fifty-four girls affected by ICPP were divided into 2 groups. The first group (30 girls) was treated with triptorelin (3.75 mg, i.m. injection) every 28 days. The second group (24 girls) was treated with cyproterone acetate and triptorelin: cyproterone acetate (50 mg/m 2 ) was administered every day for 8 weeks, and triptorelin (3.75 mg) was commenced 4 weeks after starting the cyproterone, then the intramuscular injection of triptorelin was repeated every 28 days. Results: Eight of 54 girls (15%) had mild withdrawal bleeding. There were no differences in incidence between groups 1 and 2. Girls with pubertal uterus at pelvic ultrasound had a higher incidence of uterine bleeding than girls with infantile uterus (25 vs. 7%), but this difference was not significant. Conclusion: Co-administration of cyproterone acetate and GnRH analogues does not significantly decrease the incidence of uterine bleeding.