Utility of a 40-minute LH level after depot leuprolide for diagnosis and treatment monitoring in girls with CPP

Purpose Gonadotropin-releasing-hormone (GnRH) stimulation test is used for assessment of gonadotropic activation in patients with central precocious puberty (CPP). However, it is invasive and GnRH preparation is not available in all countries. Depot-leuprolide acetate (dLA), used for the treatment of CPP, stimulates gonadotropins briefly before suppressing them. This study aimed to evaluate the utility of luteinizing hormone (LH) level measured 40-minutes after dLA injection for assessing gonadotropic activation compared to GnRH stimulation test. Methods In this prospective study, girls with idiopathic CPP were randomized to receive dLA 3.75 mg/4 weeks IM, 11.25 mg/12 weeks SC or 11.25 mg/12 weeks IM. A standard GnRH test was performed before (baseline) and after 6 months of treatment. Forty minutes after the first dLA injection, LH and follicle-stimulating hormone (FSH) levels were measured, and the same measurements were repeated after 6 months of treatment. Results The study recruited 132 girls. Peak LH on the GnRH test did not differ from the 40-minute-post-dLA LH levels [11.0(6.8–17.1) vs. 9.4(5.8–16.6); p = 0.06]. There were no significant differences between the treatment groups. Using the GnRH test peak of LH ≥ 5 IU/L as the gold-standard, ROC analysis identified the optimal cut-off of post-dLA injection LH ≥ 5.4 IU/L on initial measurement (sensitivity = 86%, specificity = 90% and AUC = 0.91). At 6 months, peak LH levels in treatment groups were similarly suppressed (2.1 ± 1.6, 2.5 ± 1.8, 2.2 ± 0.9; p = 0.2011). Furthermore, post- dLA LH cut-off of < 3.07 IU/L yielded an AUC = 0.83, sensitivity = 80.8% and specificity = 75.5%. Conclusion The 40-minute post-dLA LH provided clinically useful information concerning gonadotropic activity for both diagnosis and treatment monitoring and may provide a practical and clinically informative alternative in selected settings, particularly when standard GnRH testing is not readily available.