Diagnostic utility of testosterone priming prior to dynamic tests to differentiate constitutional delay in puberty from isolated hypogonadotropic hypogonadism in boys

Abstract Background Differentiation between isolated hypogonadotropic hypogonadism (IHH) and constitutional delay in puberty (CDP) throughout adolescence can be challenging for doctors. This study examines the withdrawal effects of short-term, low-dose testosterone treatment (testosterone priming) on the ability of dynamic testing to distinguish between CDP and IHH based on activation of the hypothalamo-pituitary–testicular axis. Methods A case–control study included 20 boys with delayed puberty (group A) and 20 patients with IHH (group B). Both groups underwent Triptorelin and human chorionic gonadotropin (hCG) stimulation tests before and 2 months after testosterone injections (100 mg) intramuscularly every 4 weekly for 3 months. Results The triptorelin-stimulated 4-h LH with a cutoff of 2.4 IU/L and the hCG-stimulated testosterone with a cutoff of 1.160 ng/mL had sensitivities of 65% each, and specificities of 90% and 95%, respectively, to diagnose CDP. After testosterone withdrawal, the cut-off values for 4-h LH were 8.850 IU/L and 3.190 ng/mL for hCG-stimulated testosterone. Basal inhibin B > 88.25 pg/ml was found to be a differentiating factor in diagnosing CDP after testosterone withdrawal. Conclusions following the withdrawal of testosterone therapy, Inhibin B levels or 4-h stimulated LH are the most effective discriminant assays to distinguish CDP from IHH.