OBJECTIVETo study the value of basal serum gonadotropin levels in the diagnosis of precocious puberty (PP) in girls.

METHODSA total of 77 girls with PP were divided into central PP (CPP) (n=45) and isolated premature thelarche (IPT) groups (n=32) based on the results of gonadotropin releasing hormone (GnRH) stimulation test, which was considered the gold standard for diagnosis of PP. The two groups were compared with respect to basal serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels and LH/FSH ratio. The receiver operating characteristic (ROC) curve was used to analyze the accuracy of basal LH and FSH levels and LH/FSH ratio in the diagnosis of PP.

RESULTSThe basal serum LH and FSH levels and LH/FSH ratio in the CPP group were significantly higher than in the IPT group (P<0.01). The basal serum LH level was positively correlated with peak LH level in the GnRH stimulation test in both groups. For diagnosis of CPP, the area under the ROC curve (AUC) for basal serum LH level was larger than for basal serum FSH level and LH/FSH ratio (P<0.05), and there was no significant difference in the AUC value between basal serum FSH level and LH/FSH ratio. When the basal serum LH level was 0.62 IU/L, there was a maximum Youden index (0.684), with 77.8% sensitivity and 90.6% specificity. When the basal serum LH level reached 1.5 IU/L, the sensitivity decreased to 31.1%, but with the highest specificity (100%).

CONCLUSIONSBasal serum LH level is superior to LH/FSH ratio and basal serum FSH level in the diagnosis of CPP, and can be used for preliminary diagnosis of PP in girls in the out-patient department, but there is some misdiagnosis and missed diagnosis. When basal serum LH level is higher than 1.5 IU/L the diagnosis of CPP can be confirmed in combination with clinical manifestation, without the need for an additional GnRH stimulation test.