BACKGROUND Peak gonadotropin-releasing hormone or agonist (GnRHa) stimulated luteinizing hormone (LH) testing with leuprolide acetate (LA) is commonly used to document suppression during therapy for central precocious puberty (CPP). The objective of the study was to investigate suitability of using basal LH levels to monitor GnRHa treatment and to determine optimal transition from 1-month to 3-month LA formulations via a post hoc analysis of a randomized, open-label, 6-month study. METHODS A total of 42 children with CPP, pretreated with 7.5-, 11.25-, or 15-mg 1-month LA formulations were randomized to 11.25- or 30-mg 3-month LA. Basal LH/peak-stimulated LH levels were measured at weeks 0, 4, 8 and 12. Positive/negative predictive values and sensitivities/specificities were determined for basal LH vs. LH-stimulation results. RESULTS Pretreatment with any 1-month formulation for the most part did not affect continuation of suppression after transitioning to 3-month formulation (mean peak-stimulated LH levels remained < 4 IU/L). Basal LH predicted suppression escape (basal LH-level cutoff ≥ 0.6 IU/L predicted 70% of those failing suppression). Tolerability was similar, regardless of dose. CONCLUSIONS Our data indicate that a basal level of <0.60 IU/L is adequate for monitoring suppression approximately two-thirds of the time. Furthermore, the effectiveness and safety of 3-month LA treatments are not influenced by previous CPP therapies.