The best way to measure whether treatment of children with central precocious puberty is working is to do a hormone stimulation test (leuprolide stimulation test) that requires injection of a medication and multiple blood draws to see if the hormonal response is suppressed (blocked). The hypothesis of this study is that random measurement of the free alpha subunit of pituitary glycoprotein, a protein related to the pituitary hormones that stimulate puberty, will provide an adequate alternative to the leuprolide stimulation testfor monitoring efficacy of pubertal suppression with Supprelin LA®.