ESPE Abstracts

Background: The hypothalamus-pituitary-gonad (HPG) axis is crutial to the development and function of reproductive system. Gonadotropin-releasing hormone (GnRH) has been the standard test for the assessment of activation of HPG axis. Because GnRH is no longer available, GnRH analogues (GnRHa) are now used. In previous studies, GnRHa stimulation tests have been the mainstay for establishing the diagnosis of precocious puberty in female and distinguishing constitutional delay of growth and puberty from isolated hypogonadotropic hypogonadism in male patients. Neither the clinical values of GnRHa tests in evaluating the activation of HPGA across the pubertal transition, nor the optimal sampling times for luteinzing hormone (LH) have not yet to be established.

Objective and hypotheses: To investigate the clinical values of GnRHa (Triptorelin) stimulation test in the evaluation of the activation of the HPGA in boys and to provide a scientific method in the early diagnosis of puberty onset in boys. And to determine the appropriate sampling time for LH post triptorelin challenge.

Method: A prospective study of multi-sample GnRHa stimulation tests were performed in 68 boys. Based on the testicular volume (≧4 ml) and serum testosterone (≧0.2 ng/ml), they were divided into two groups, in which 30 boys with prepuberty and 38 boys with puberty. After 3 mcg/kg of Q7 Triptorelin, samples were obtained at 0, 1, 3, 6 hours. The 68 stimulation tests were reviewed and analysed. For each parameter, the sensitivities and specificities were estimated and ROC curves were constructed.

Results: Both serum Follicle-Stimulating Hormone (FSH) and LH concentrations were different at 0, 1, 3, 6 hour after GnRHa tests in prepubertal group and pubertal group. In prepubertal group, ΔFSH was much higher than ΔLH. In pubertal group, ΔLH was much higher than ΔFSH. No differences were found among the serum ΔFSH or peak FSH between two groups. There are differences among either peak LH or peak LH/FSH in prepubertal and pubertal groups. The measurement of peak LH≧13.98 IU/L and peak LH/FSH≧0.92 had rather high sensitivity (81.5%) and specificity (86.7%) for distinguishing pubertal boys from those in prepubertal stage. Percentages of peak LH after GnRHa tests appeared at 1, 3, 6 h in a total of 68 cases were 10%, 68% and 22%, respectively.

Conclusion: Triptorelin stimulation test appears to have a great value in the assessment of the activation of HPGA in boys. The measurement of both peak LH and LH/FSH has rather high sensitivity and specificity in diagnosing puberty onset. A single serum LH sample collected 3 hours post GnRHa challenge is the optimal sample to establish the diagnosis of puberty onset.