Predictive value of luteinizing hormone releasing hormone (LHRH) bolus testing before and after 36-hour pulsatile LHRH administration in the differential diagnosis of constitutional delay of puberty and male hypogonadotropic hypogonadism.

Intravenous LHRH bolus testing (100 micrograms) after 36 h of pulsatile LHRH administration (5 micrograms/90 min) preliminary has been reported to allow complete differentiation between constitutional delay of puberty (DP) and hypogonadotropic hypogonadism (HH) in a small group of sexually immature patients. So far, these data have never been confirmed. To assess the discriminatory power of the test, 33 patients with a presumptive diagnosis of either DP (n = 17) or HH (n = 16), confirmed by clinical follow-up, were studied accordingly. Both groups of patients had similar mean basal LH and FSH levels (P > 0.10). The mean basal plasma testosterone level was three times higher in DP than in HH (4.2 +/- 1.0 vs. 1.4 +/- 0.2 nmol/L, P* < 0.001), but there was a wide overlap. In response to the first LHRH bolus test, the mean LH increment was significantly lower in HH than in DP patients (P < 0.001), but, in 44% of the patients, the values overlapped. The FSH increments were similar in HH and DP. Pulsatile LHRH administration for 36 h similarly increased LH levels in HH and DP to values (2.7 +/- 0.4 and 3.8 +/- 0.5, respectively) slightly higher than before (P < 0.01), but again, not statistically significantly different from each other. The mean testosterone levels increased 2-fold in both groups and remained significantly higher in DP than in HH (7.6 +/- 2.1 vs. 2.8 +/- 0.5 nmol/L P* < 0.05). The mean FSH levels after priming also rose, however, to levels significantly higher in HH than in DP (5.2 +/- 0.8 vs. 3.5 +/- 0.4, P* < 0.05). In HH the ratio of FSH to LH almost doubled, whereas it virtually remained unchanged in DP. LHRH bolus testing after LHRH priming evoked a significantly lower LH response in both HH and DP than before priming despite only slightly higher baseline LH values. The LH increment in HH was five times lower in HH than in DP. In any of the 16 HH patients, the LH increment was < or = 3 IU/L, whereas in 15 out of 17 DP patients the increase was higher (sensitivity of the test 100%, specificity 88%, and diagnostic efficiency 94% after LHRH priming against 56%, 94%, and 75% respectively, before LHRH priming.(ABSTRACT TRUNCATED AT 400 WORDS)