Diagnostic accuracy of the triptorelin stimulation test for central precocious puberty in girls

Abstract: Central precocious puberty (CPP) results from premature activation of the hypothalamic-pituitary-gonadal axis. The GnRH stimulation test remains the diagnostic gold standard, especially in girls with undetectable basal LH levels. However, native GnRH is expensive and often unavailable. Rapid-acting subcutaneous triptorelin has been proposed as a reliable alternative. This retrospective study evaluated the diagnostic accuracy of subcutaneous triptorelin compared with intravenous gonadorelin and investigated the optimal timing for LH peak assessment. A total of 341 girls referred for suspected precocious puberty were evaluated: 102 underwent the triptorelin test and 239 the gonadorelin test, with gonadotropins measured by electrochemiluminescence assay at baseline and after stimulation. Based on clinical, radiological, and laboratory criteria, 143 girls were diagnosed with CPP and 198 with non-progressive thelarche (NPT). Triptorelin elicited significantly higher FSH peaks than gonadorelin, while LH peaks were comparable; consequently, FSH/LH ratios were higher after triptorelin. ROC analysis identified an optimal diagnostic LH peak cut-off of 7.14 IU/L following triptorelin administration (sensitivity 94%, specificity 96%; AUC 0.985), while a threshold of 4.7 IU/L was observed after gonadorelin (sensitivity 100%, specificity 87%; AUC 0.982). Peak LH occurred predominantly at 180 min after triptorelin in both CPP and NPT groups (78 and 90%, respectively). Despite the limitations of its retrospective and non-parallel design, this large cohort study demonstrates that subcutaneous triptorelin provides excellent diagnostic accuracy, comparable to gonadorelin. These findings support triptorelin as a reliable and accessible alternative for CPP diagnosis and contribute to the standardization of diagnostic protocols in clinical practice. Plain language summary: This study tested triptorelin stimulation as an alternative to the standard gonadorelin test to diagnose precocious puberty in girls. Triptorelin proved equally accurate and reliable, especially when hormone levels are measured 3 h after injection, offering a practical diagnostic tool in clinical practice.