Usefulness of GnRH infusion test in the diagnosis of boys with delayed puberty

GRINSPON R; REY R.; GOTTLIEB S.; KESELMAN A.; MARTINEZ A.; BALLERINI G; DOMENÉ H; ROPELATO MG

Estambul. Turquía

Congreso; 47th Annual Meeting of the ESPE Estambul. Turquía; 2008

ESPE

In boys who present with delayed puberty, the differential diagnosis between hypogonadotropic hypogonadism (HH) and constitutional delay of puberty is difficult.  Although different tests have been proposed to distinguish these two conditions, no consensus exists.  The aim of this study was to evaluate the usefulness of the GnRH infusion test to predict complete or partial HH in boys presenting with delayed or arrested puberty. Thirty-five boys (16.4 ± 3.0 yr, 30 with absence of and 5 with arrested puberty) were submitted to IV GnRH infusion (0.83 ug/min for 120 min). LH and FSH were determined by IFMA at 0, 15, 30, 45, 60 and 120 min. Final diagnosis of complete HH (n=17) was done when testes were < 4 ml at 18 yr. Partial HH (n=11) was diagnosed when testes enlargement started but remained arrested for a period of at least 1 yr and did not reach 15 ml. ROC curves were used to determine the optimal cut-off points. LH peak occurred variably between 15 and 120 min after infusion start, while FSH peak occurred at 120 min in 32 of 35 patients. LH peak value <5.8 IU/L showed a 95.8 % positive predictive value (PPV) for HH, with 82% sensitivity (S) and 85% specificity (Sp); the positive likelihood ratio (LR+) was 5.8. FSH peak value <4.6 IU/L showed similar results. Interestingly, basal FSH <1.15 IU/L had a 100% PPV for HH, with 64.3% S and 100% Sp. A peak LH >5.8 IU/L and peak FSH >4.6 IU/L in the same patient detected delayed puberty with 85.7% S and 89.2% Sp; the LR+ was 8. The ratio between peak LH and peak FSH did not add any further useful information. In conclusion, in a boy with delayed or arrested puberty, a low basal FSH value confirms a diagnosis of HH with high accuracy, and no further test is necessary. A subsequent GnRH infusion test is useful to confirm HH when peak LH or peak FSH are below selected cut-off values. When both peak values are above cut-off values in the same patient, a constitutional delay of puberty can be diagnosed with high accuracy.