The gonadotropin-releasing hormone (GnRH) test results of girls with precocious puberty were analyzed to determine whether this test can efficiently and clearly differentiate between central precocious puberty (CPP) and other disorders.

Clinical and laboratory data of 54 girls with precocious pubertal signs were reviewed. Intravenous GnRH test was performed with blood samples obtained at 0, 30, 60, and 90 minutes. A peak luteinizing hormone (LH) level of ≥5.0 IU/L was indicative of CPP.

Of the 40 girls with CPP, 36 (90.0%), 3 (7.5%), and 1 (2.5%) showed peak LH levels at 30, 60, and 90 minutes, respectively. A percentage of girls whose peak LH ≥5.0 IU/L up to 30, 60, and 90 minutes was 92.5%, 100%, and 100%, respectively. The peak LH/follicle stimulating hormone (FSH) ratio of girls with CPP was 0.89±0.49 and was <1 in 16 of the 40 girls (40.0%). Girls with peak LH/FSH ratio of >1.0 showed higher chronological age (CA) (8.3±0.6 vs. 7.7±1.0 years, P =0.033), bone age (BA) (10.9±0.8 vs. 9.7±1.1 years, P =0.001), and BA-CA difference (2.6±0.7 vs. 2.0±0.7 years, P =0.009) than those of girls with peak LH/FSH ratio of ≤1.0. Higher percentage of girls with peak LH/FSH ratio of >1.0 showed advanced breast development (≥Tanner III) (93.7% vs. 41.7%, P =0.001).

LH levels after 30 and 60 minutes of intravenous GnRH administration are the most useful for diagnosing CPP in girls.