The diagnostic value and optimal cutoff of basal luteinizing hormone for central precocious puberty in premenarcheal girls stratified by weight status.

OBJECTIVE: To investigate the diagnostic value and explore optimal cutoff value of the basal luteinizing hormone (LH) level for central precocious puberty (CPP) in premenarcheal girls with different weight status, so as to provide preliminary stratified reference thresholds and a basis for reducing unnecessary gonadotropin-releasing hormone (GnRH) stimulation tests in clinical screening. METHODS: This retrospective single-center study involved girls with breast development. They were divided into groups of normal weight (n=982), overweight (n=381), obesity (n=195) and underweight (n=176) based on body mass index (BMI) z scores. All individuals underwent GnRH stimulation test. General characteristics and hormonal profiles were compared among different weight groups, and receiver operating characteristic (ROC) curves were plotted. RESULTS: In each weight group, CPP girls had significantly higher basal LH, bone age, and uterine/ovarian volumes than non-CPP girls, and basal LH showed moderate positive correlations with peak LH (Spearman's rho ranged from 0.557 to 0.633, all P<0.05). Basal LH had a higher area under the curve (AUC) for CPP diagnosis than basal FSH and LH/FSH ratio across all groups, with the AUC values of basal LH being 0.770 (normal weight), 0.822 (overweight), 0.749 (obesity), and 0.767 (underweight). The optimal basal LH cutoffs derived from the maximum Youden index were 0.165 IU/L (normal weight), 0.145 IU/L (overweight), 0.135 IU/L (obesity) and 0.135 IU/L (underweight), with the corresponding Youden indices of 0.402, 0.525, 0.416, and 0.456, respectively. At these thresholds, the sensitivity of basal LH for CPP diagnosis ranged from 45.8% to 84.4% and specificity ranged from 63.6% to 70.4% across all subgroups. CONCLUSIONS: Basal LH serves as a convenient indicator with moderate diagnostic discrimination for CPP screening in premenarcheal girls with different weight statuses, and weight-stratified optimal cutoffs provide individualized screening references for girls with different weight statuses and help mitigate diagnostic bias caused by body weight confounding.