Endocrine Abstracts

Introduction: Central precocious puberty (CPP) is rarer in boys than girls, therefore evidence is limited for interpreting LHRH testing in boys. Current recommendations also suggest use of basal LH.

Objectives: i) Test efficacy of using basal LH and testosterone for predicting CPP in boys. ii) Establish diagnostic cut-offs for LHRH testing in boys.

Method: Retrospective data collection of LHRH test results in 67 boys aged 2–10 years old, from a regional paediatric centre between 2005 and 2013.

Measure of progression into puberty based on clinician’s judgment following LHRH testing: ten boys in progression group and 57 boys in non-progression group.

Results: Statistically significant difference between the basal LH, LHRH-stimulated LH levels and stimulated LH/FSH ratio between the groups.

Using basal LH ≥0.3 IU/ as cut-off yielded 60% sensitivity, 80.7% specificity and NPV 92.0%. In addition, using basal testosterone ≥3.3 nmol/l produced 83.3% PPV and 91.4% NPV, 98.2% sensitivity. There was, however, no correlation between testicular volumes and testosterone level.

Different diagnostic cut-offs were found which have not been previously reported: >5.3 IU/l for stimulated LH level at 30 min and >3.5 IU/l at 60 min; stimulated LH/FSH ratio >1.26 at 30 min and >1.0 at 60 min respectively.

Stimulated LH/FSH at 60 min was found to be have the most diagnostic value with 100% sensitivity (95% CI: 71.3–100%), 94.6% specificity (85.1–98.8%) and 100% NPV (93.2–100%).

Conclusion: Using basal LH and testosterone together can be a useful screening test to rule out CPP in boys. If a LHRH test is required; we report new diagnostic cutoffs, and have shown that the stimulated LH/FSH ratio provides the greatest diagnostic value.