Evaluation of gonadotropin responses and response times according to two different cut-off values in luteinizing hormone releasing hormone stimulation test in girls

Background: In this study, we aimed to evaluate FSH, LH responses obtained during LHRH-ST according to two different cut-off values, to determine the diagnostic response times, and to find the optimal blood collection times that could reduce the economic and time burden of LHRH-ST. Materials and Methods: Patients who underwent LHRH-ST in our clinic with the preliminary diagnosis of precocious puberty (PP) between 01/08/2016 and 31/12/2017 were retrospectively enrolled to the study. In this study 207 girls with PP were included and some of them (102 according to C1 and 139 according to C2) had central PP (CPP). Test response and response times were evaluated according to both cut-off values of stimulated peak LH pubertal responses as 5 mIU/ml (the 1st cut-off = C1) and 3.3 mIU/ml (the 2nd cut-off = C2). Results: Totally, 207 girls with a mean age of 7.5 ± 1.22 (3.4-9.5) years were included in the study. With LHRH-ST; 49.2% (n = 102), 67% (n = 139) of the cases were in pubertal period according to C1, C2, respectively. According to C1; pubertal LH was present in 94.1% (n = 96) of 102 patients who reached pubertal LH value in 45th minutes. The highest pubertal response was obtained in the 45th minute. According to C2, of 139 patients who reached pubertal LH; pubertal LH was determined in 98.5% (n = 137) in the 45th minute. Pubertal LH levels were determined according to both cut-off values in all 27 patients with baseline LH ≥0.31 mIU/ml. Conclusion: It was determined that measuring LH at 45th minutes during LHRH-ST was sufficient in 94.1% of the cases according to C1 and 97.1% of the cases according to C2. It was concluded that the 30th, 45th, and 60th minute samples were enough to assess pubertal LH response in 100%of the cases. If the basal LH is found to be ≥0.31 mIU/ml in girls with puberty findings, we recommend that the diagnosis of precocious puberty would be made without performing LHRH-ST.