ESPE Abstracts

Introduction: Central precocious puberty (PPC) is defined by the appearance of sexual characters at a chronological age lower than -2.5DS of the average for the reference population. Diagnostic is clinical but the hormonal assessment is essential. Basal gonadotropin values are not enough for the diagnosis. Gonadotropin-releasing hormone (GnRH) stimulation tests evidence the activation of the hypothalamic-pituitary-gonadal axis, however there is controversy about the optimal cut-off points to define a progressive PPC.

Objectives: Due to method change, the objective were to evaluate the usefulness of the GnRH test for the diagnosis of PPC and to define the optimal cut-off point for a progressive PPC with the methodology used in our laboratory.

Methods: Descriptive, prospective study. 55 patients (52 women) visited for suspected precocious puberty during the years 2020-2022. The evaluation included: anthropometric parameters, basal hormonal analysis, bone age, ultrasound of internal genitalia and GnRH test. According to clinical evaluation the cohort was divided in two groups: progressive puberty (PP) and non-progressive puberty (NPP). The LHRH test was carried out with basal LH, FSH, Estradiol and testosterone determinations and LH and FSH at 15, 30, 60 and 90 minutes after the administration of 0.1mg of LHRH IV. Serum hormones were measured with Architect i200 immunoassay (Abbot diagnosis). Data between both groups were compared with Mann-Whitney U and ROC curves are used to calculate the discriminatory cut-off points (MedCalc19.6).

Results: As expected, the determination of gonadotropins is the one that best discriminates a PP, being higher in this group. The other parameters did not obtain significant differences between groups. asal and stimulated LH, basal FSH and the basal and stimulated LH/FSH quotient were significantly higher in PP-Group (P<0.05). A basal concentration of LH > 0.48mUI/L has 100% specificity for the diagnosis of progressive PPC, with a sensitivity of 50%. The optimal cut-off points in the GnRH test to diagnose a PPC are LH at 30 minutes >5.1mUI/L (S84.62, E92.59. AUC 0.937) and LH/FSH at 60 minutes >0.35 (88.46, E96.3. AUC 0.946).

Conclusions: A basal LH of > 0.48mIU/L is 100% specific for progressive PPC, this would prevent the performance of a stimulation test in these cases. The stimulated LH at 30 minutes and the LH/FSH quotient at 60 minutes are the optimal predictors of PPC in our cohort. GnRH test could be simplified, intermediate or longer points do not contribute more sensibility according to our study.