Session: OR37-Pediatric Endocrinology: HPG Axis Disorders
Room 102 (Moscone Center)
The clinical distinction between constitutional delay of growth and puberty (CDGP) and isolated hypogonadotropic hypogonadism (IHH) in males with delayed puberty is difficult. Definitive diagnosis by endocrine testing is important for counselling and especially, for treatment in time.
We assessed the accuracy of the GnRH agonist challenge in comparison to basal inhibin B (INHB) and basal LH for diagnosing IHH in a prospective study.
Prepubertal males (n=50) with an age between 13.6 and 16.5 years and a testicular volume ≤ 3.5 ml were recruited. CDGP was defined by reaching a testicular volume ≥ 8 ml during an 18 months follow-up while a testicular volume < 8 ml after 18 months was taken as indicative of the presence of IHH. INHB was measured by ELISA (Beckman Coulter, Inc, U.S.A), LH by CLIA (Siemens Health Care Systems, Germany). We assessed the test validity of basal LH and basal INHB as well as of stimulated LH at 4h (LH(4h)) after a Triptorelin 0.1 mg challenge.
The cohort comprised 42 boys with CDGP and 8 with IHH. Each, basal LH<0.3 IU/L or LH(4h)<5.6 IU/L or INHB<112 pg/mL had a sensitivity for the detection of IHH of 100%. However, only LH(4h)<5.6 IU/L had a specificity of 100% while specificities of basal LH<0.3 IU/L (86%) and of INHB<112 pg/mL (92%) were lower. The combination of both basal parameters, LH<0.3 IU/L plus INHB<120 pg/mL, increased the specificity to 95%.
The area under the curve of ROC plot analysis for diagnosing IHH was greatest for LH(4h)<5.6 IU/L (100%) followed by INHB<112 pg/mL (98%; 95%-CI: 96%-100%) and basal LH<0.3 IU/L (95%; 95%-CI: 90%-100%).
The LH response 4 hours after GnRH agonist challenge has an excellent sensitivity and specificity to diagnose IHH in prepubertal boys with delayed puberty. In the absence of GnRH agonist challenge, the combined judgement of basal LH and INHB is a valid alternative with a slightly lower specificity. We recommend the GnRH agonist challenge to diagnose IHH in boys with delayed puberty.
Nothing to Disclose: GB, RS, RB
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