ESPE Abstracts

Context: Intravenous Gonadotropin-Releasing-Hormone (GnRH) stimulation test has a central role in evaluating gonadotropic activation in the diagnosis and monitorization of the treatment in patients with central precocious puberty (CPP). However, this test is invasive, laborious, costly and availability of GnRH preparation is limited in some countries.

Objective: To evaluate the utility of the LH level measured 40-minutes after intramuscular depot-Leuprolide acetate(dLA) injection, in assessing gonadotropic activation.

Methods: In a prospective study, 92 girls with CPP were randomized to receive ıntramuscular dLA 3.75 mg/4 weeks (Group-1, n=47) or 11.25 mg/12 weeks (Group-2, n=45). A standard GnRH stimulation test was performed before- and at 6 months of treatment to assess gonadotropin suppression. Basal and 40-minute post-dLA gonadotropins and estradiol were measured at the beginning and at the 6th month of treatment

Results: There was no difference in clinical, and hormonal characteristics of Group-1 and Group-2 at the onset of treatment. At the beginning of treatment, mean peak LH in the GnRH test (16,2±16,3 vs 13,5±9,8 mIU/mL) and 40-minute post-dLA injection LH (16,8±18,2 vs 13,2±13,4 mIU/mL) were similar for Group-1 and Group-2, respectively. At 6 months, peak LH levels were similarly suppressed to 2,1±1,6 vs 2,2±0,9 mIU/mL in the GnRH test, and 2,9±1,9 vs 2,9±1,2 mIU/mL in 40-minute post-dLA injection for Group-1 and Group-2, respectively. Mean GnRH-stimulated LH levels and 40-minute post-dLA LH levels did not differ between the groups during treatment. Peak LH at GnRH test and 40-minute post-dLA injection LH were strongly correlated at the beginning (r:0.68, P<0.001) and at the 6 months (r:0.74, P<0.001) of treatment. 89% of the patients whose peak LH >5 mIU/mL on GnRH test at diagnosis, also had a 40-minute post-dLA LH >5 mIU/mL. At the 6 months of treatment, 7 patients in Group-1 and 10 patients in Group-2 had peak LH >3 mIU/mL in GnRH test (suboptimal suppression). In 88% of these patients, 40-minute post-dLA LH was also >3 mIU/mL confirming suboptimal suppression.

Conclusion: Long-acting GnRH analogues used in the treatment of CPP stimulate LH for a short time as strongly as intravenous GnRH. A single LH measurement 40 minutes after the first dose of depot dLA and at 6 months of treatment provides ample information about the gonadotropic activity comparable to a standard intravenous GnRH test before and during treatment.