ESPE Abstracts

Background: Existing tests are not 100% accurate in differentiating between isolated hypogonadotropic hypogonadism (HH) and constitutional delay of puberty (CDP) in boys. Inhibin B is a glycoprotein produced by the Sertoli cells and is measurable even before puberty. Its level increases at the beginning of puberty under the influence of FSH.

Objective and hypotheses: The levels of inhibin B (InhB) could differentiate between HH and CDP. We aimed to establish a cut-off value for InhB which can distinguish between CDP and HH in boys.

Method: We analyzed 18 boys with delayed puberty: ten with CDP-genital stage1 (CDP-G1) and eight with HH. We studied: auxometrical parameters, testicular volume, basal InhB, AMH, FSH, LH, testosterone and stimulated values of FSH, LH and testosterone after the soluble sc Triptorelin test.

Results: The comparison between the CDP and the HH groups revealed that basal InhB, and LH levels at 4 h after the Triptorelin test were significantly lower for the HH group. The ROC curve for the CDP and HH groups shows that an InhB level <29.2 pg/ml has 100% specificity and 60% sensibility for diagnosing HH, and InhB level >78.1 pg/ml indicate CDP with 100% specificity.

Conclusion: Basal InbB concentrations are the most reliable in identifying the patients that suffer from hypogonadotropic hypogonadism. Moreover, it aids in cost reduction, since Triptorelin sc testing will only need to be performed for patients with InhB values in the grey zone (29.2–78.1 pg/ml).