Use of GnRH agonist and human chorionic gonadotrophin tests for differentiating constitutional delayed puberty from gonadotrophin deficiency in boys

Summary objectives The differentiation of constitutional delayed puberty (CDP) from gonadotrophin deficiency (GD) in boys at referral poses a difficult challenge. The effectiveness of the GnRH agonist (GnRH‐a) test in distinguishing between the two conditions was evaluated and compared with findings of the GnRH and hCG stimulation tests. patients, methods and design The study sample included 32 prepubertal boys aged 14 years or older. Thirteen entered spontaneous puberty within 1 year of referral (group A) and 19 remained prepubertal (group B). All underwent the GnRH test (Relefact, Hoechst AG, 0·1 mg/m2 i.v. in one bolus), GnRH‐a test (Decapeptyl, Ferring GmbH, 0·1 mg/m2 s.c.) and hCG stimulation (Chorigon, Teva, 1500 units i.m. on three alternate days) at 1‐week intervals. All tests were performed at referral at 0800 h. Blood samples were collected before testing and at 30 and 60 min (GnRH test) or 4 h (GnRH‐a) for LH and FSH determination, and before testing and at 4 h (GnRH‐a) or on the seventh day (hCG) after stimulation for serum testosterone measurement. results The LH response to GnRH‐a and the testosterone response to hCG stimulation were significantly higher in group A (LH, mean ± SD 20·4 ± 7·5 mIU/ml, range 10·8–32·6; testosterone, mean ± SD 18·0 ± 5·9 nmol/l, range 9·4–26, P