IMPE Abstracts

Introduction: Central precocious puberty (CPP), the development of secondary sex characteristics before ages 8 and 9 years in girls and boys, is caused by premature activation of the hypothalamus-pituitary-gonadal (HPG) axis. A gonadotropin-releasing hormone stimulation (GnRH test) is the gold standard diagnostic method to confirm activation of the HPG axis and peak LH levels higher than 5 IU/L are considered a pubertal response. However, the GnRH test is expensive, time-consuming and not always available.

Objective: To analyze the diagnostic accuracy of basal LH and LH/FSH ratio for CPP diagnosis measured by immunochemiluminescence assay, LH peak level post GnRH test > 5 mU/ml was considered as indicator of HPG axis activation status.

Methods: Data from 118 children, 103 (87,3%) girls under 8 years and 15 (12,7%) boys under 9 years who underwent GnRH agonist stimulation testing between April 2020 to August 2022 were retrospectively reviewed. Age, sex, LH and FSH at 0, 30, 60 and 90 min after GnRH, as LH/FSH basal ratio, were recorded. Statistical analysis: correlations were estimated with beta coefficients from linear regression models, with P<0.05 as significant. The ROC, sensitivity, specificity and predictive values with logistic models, 95% confidence intervals are reported.

Results: Basal LH showed a positive correlation with peak LH in girls (P<0,001, R2=0,21) but not in boys (p 0,227, R2 0,11). LH/FSH also correlates with peak LH in girls (p 0,027, R2=0,05). In girls sensitivity with basal LH cut-off at 0.1 - 0.3 - 0.6 and 0.8 IU/L were 81.6 - 51 - 34.6 and 30.6% respectively. Specificity was 33.3 - 70.3 - 90.7 and 94.4% respectively. Basal LH > 0.86 IU/L specificity was 96.3%. In boys, basal LH > 0,28 IU/L had 100% sensitivity and 81.8% specificity, but the little sample size must be considered.

Conclusions: Although basal LH and LH/FSH values correlate with LH peak after GnRH test in girls, its sensitivity and specificity are not accurate enough to predict activation of HPG axis. With classical cut-off point of 0.1 and 0.3 UI/L. Only basal LH >0.86 IU/L may not require GnRH test and in most cases, GnRH test is still necessary to confirm the diagnosis of central precocious puberty.