Single random measurement of urinary gonadotropin concentration for screening and monitoring of girls with central precocious puberty

The gold standard for assessing pubertal activation is the gonadotropin-releasing hormone (GnRH) stimulation test (GnRHST), which is invasive, time-consuming and inconvenient. This study evaluated whether a single random measurement of urinary luteinizing hormone (LH) concentration could substitute for the GnRHST in diagnosing and monitoring central precocious puberty (CPP) in girls. Fifty-five girls with breast buds before 8 years of age were assessed by both the GnRHST and urinary gonadotropin assays. Based on GnRHST results, 29 girls were assigned to the CPP group (peak LH ≥ 5 IU/L) and 26 to the premature thelarche (PT) group (peak LH < 5 IU/L). Auxological data and urine and serum samples were collected at baseline and after treatment with GnRH agonist for 12 and 24 weeks. Although auxological data did not differ between the two groups, the levels of insulin-like growth factor-1, basal LH and follicle stimulating hormone (FSH), estradiol, peak LH, urinary LH, and peak LH/FSH and urinary LH/FSH ratios were higher in the CPP than in the PT group. Pearson's correlation analysis showed a positive correlation between urinary and serum LH concentration (r = 0.660, P < 0.001). Receiver-operating characteristic curve analyses showed that urinary LH concentration 0.725 IU/L was a cutoff significantly reflecting positivity on the GnRHST. Urinary LH and FSH concentrations declined significantly during GnRH agonist treatment. A single, random measurement of urinary gonadotropin concentration may be reliable for the initial screening and monitoring of CPP in girls.