To investigate the predictive power of basal luteinizing hormone (LH) level for central gonadal activation states in girls.

A total of 343 girls who developed secondary sex characteristics before the age of 8 years old and were hospitalized in the Affiliated Hospital of Jining Medical University from February 2015 to August 2022 were included in this study. The general clinical data were collected and the gonadotropin-releasing hormone analogue (GnRHa) stimulation test was performed. Based on the peak of LH in the GnRHa stimulation test, these girls were categorized into three groups: premature thelarche (PT), partial central precocious puberty (CPP), and complete CPP. The Logistic regression was used to clarify the independent correlation factors of PT and complete CPP. Receiver operating characteristic (ROC) curve was applied to compare the predictive power of the independent factors for PT and complete CPP.

Basal LH level showed significant differences between PT, partial CPP, and complete CPP groups with quartiles of 0.06(0.01, 0.16)U/L, 0.30(0.12, 0.56)U/L, and 1.50(0.72, 2.83)U/L, respectively. The difference between the three groups was meaningful in statistic (H=164.74, P<0.01). Age, basal LH, estradiol level, and uterine volume were independent influential factors of PT. Basal LH, estradiol level, and uterine volume were independent influential factors for complete CPP. Basal LH level was the best predictor for PT and complete CPP with AUCs of 0.874 and 0.878, respectively. The optimal cut-points of basal LH level for predicting PT and complete CPP were 0.185 U/L (sensitivity 83.90%, specificity 75.90%) and 0.435 U/L (sensitivity 80.50%, specificity 84.10%), respectively.

Basal LH level is a valuable predictor of central gonadal activation states in girls, and can be used as an early screening index for CPP.