Treatment of central precocious puberty: comparison of urinary gonadotropin excretion and gonadotropin-releasing hormone (GnRH) stimulation tests in monitoring GnRH analog therapy.

GnRH analogs (GnRH-a) have proven to be efficacious and have become the standard treatment for central precocious puberty (CPP). To confirm the diagnosis of CPP and to monitor the adequacy of hvpothalamic-pituitary-gonadal (HPG) axis suppression, GnRH stimulation testing has been essential. To determine whether 24-h urinary gonadotropin excretion could adequately assess HPG axis suppression, we compared the results of simultaneous GnRH stimulation tests and 24-h urinary gonadotropin determinations in 18 girls with CPP who were receiving GnRH-a therapy (leuprolide acetate, Depot-Lupron, TAP Pharmaceuticals). HPG axis suppression was defined as the absence of significant LH and FSH responses to GnRH stimulation. Simultaneous GnRH stimulation tests and urinary gonadotropin determinations had a concordance rate of 68% (42 of 62). The sensitivity and specificity of urinary LH determinations to detect inadequate HPG suppression were 75% and 64%, respectively. For urinary FSH determinations, the sensitivity and specificity were 90% and 28%, respectively. Hence, single timed urine collections lacked the sensitivity and specificity to assess HPG axis suppression and, thus, cannot replace GnRH stimulation tests for monitoring the adequacy of the GnRH-a dose.