Role of Inhibin B, AMH, GnRHa Test and HCG Stimulation Test to Distinguish Isolated Hypogonadotropic Hypogonadism (IHH) from Constitutional Delay in Growth and Puberty (CDGP).

Introduction: This study aimed to distinguish isolated hypogonadotropic hypogonadism (IHH) from constitutional delay in growth and puberty (CDGP) by various hormonal tests in both sexes.

Methods: Boys with testicular volume (TV) <4 ml (14-18 years) and girls with breast B₁ stage (13-18 years) were enrolled in this study. A detailed history, clinical examination and hormonal analysis including basal luteinising hormone (LH), follicle-stimulating hormone (FSH), inhibin B, anti-Mullerian hormone (AMH), testosterone (boys), oestradiol (girls), triptorelin stimulation test and 3-day human chorionic gonadotropin (HCG) stimulation test (boys) were performed. All patients were followed for 1.5 years or till 18 years of age. Receiver operating characteristic (ROC) curve analysis was performed to determine the optimal cut-offs with sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for various hormones to distinguish IHH from CDGP.

Results: Of 34 children (male: 22 and female: 12), CDGP and IHH were diagnosed in 21 and 13 children, respectively. 4 hours post-triptorelin LH had the highest sensitivity (100%) and specificity (100%) for identifying IHH in both sexes. Basal inhibin B had good sensitivity (male: 85.7% and female: 83.8%) and specificity (male: 93.3% and female: 100%) for diagnosing IHH. 24 hours post-triptorelin testosterone (<34.5 ng/dl), day 4 post-HCG testosterone (<99.7 ng/dl) and 24 hours post-triptorelin oestradiol (<31.63 pg/ml) had reasonable sensitivity and specificity for identifying IHH. Basal LH, FSH and AMH were poor discriminators for IHH in both sexes.

Conclusion: The best indicator was post-triptorelin 4-hour LH followed by inhibin B, which had a reasonable diagnostic utility to distinguish IHH from CDGP in both boys and girls.