Endocrine Abstracts

Introduction: Luteinising Hormone Releasing Hormone stimulation test (LHRH) is the gold standard test for diagnosing central precocious puberty (CPP). However, previous studies have advocated using a single LH (Luteinising Hormone) measure to diagnose CPP thus reducing the patient’s investigative burden.

Method and aims: We assessed if i) baseline LH levels predicts response on LHRH test ii) the timing of basal LH measurement influences its predictive value. A retrospective review of children undergoing LHRH testing at Bristol Royal Hospital for Children between February 2019 to January 2023 was conducted. LH was measured using Roche Sandwich Immunoassay, 3rd generation (<0.1 IU/L lower limit of detection).

Results: 111 tests were conducted (n=99 in females, n=12 in males). LH and FSH levels were measured at 30 min and 60 min after LHRH administration. Those with a peak LH ≥5 and LH predominance were categorised as positive, peak LH ≥5 but FSH (follicle stimulating hormone) predominance as borderline, and peak LH <5 was categorised as negative. Of the 28 positive tests, only 2 had baseline LH <0.3 and both were afternoon tests. Of the 70 negative tests, 2 had baseline tests LH ≥1, both morning tests. The table below summarises the predictive values for different basal LH levels.

The mean tanner breast staging was higher in positive tests; 2.86 vs 2.10 (P=<0.001). There was no significant difference in testicular volume between positive and negative tests; 3.75 mL vs 4 mL (P=0.72).

Conclusion: Using a LH cut off of ≥ 0.3 provided the best balance of sensitivity and specificity and could be used to predict a positive LHRH test in the majority of cases. False negatives were more common if using afternoon basal LH samples and false positives more common if using morning basal LH samples to predict LHRH response. LH levels should be correlated with pubertal stage as part of the clinical assessment.