Adequacy of a single unstimulated luteinizing hormone level to diagnose central precocious puberty in girls

OBJECTIVE. Using basal specimens from original gonadotropin radioimmunoassays, it was not possible to differentiate prepuberty from puberty hence gonadotropin-releasing hormone or gonadotropin-releasing hormone analog (GnRHa) testing was required to make this distinction. Third-generation gonadotropin assays have far greater specificity and sensitivity. Using a group of patients who had the diagnosis of central precocious puberty (CPP) verified or excluded by using GnRHa and traditional diagnostic criteria, the objective of this study was to determine if a single basal gonadotropin measurement was adequate to verify the diagnosis of CPP by using 2 third-generation gonadotropin assays. METHODS. Girls referred for assessment of early puberty had previously been evaluated for central precocious puberty including gonadotropin-releasing hormone analog stimulation testing with gonadotropin measurements by 2 different chemiluminescent third-generation immunoassays. Diagnosis of central precocious puberty was made on the basis of the response to the gonadotropin-releasing hormone analog, and clinical criteria. Girls with central precocious puberty had luteinizing hormone responses ranging from 9.1 to 67.6 U/L, the prepubertal luteinizing hormone response range was 0.2 to 5.0 U/L. Basal serum luteinizing hormone and folliclestimulating hormone concentrations from these girls have been assessed to determine the utility of using such a single sample to diagnose central precocious puberty. RESULTS. Basal luteinizing hormone levels using the 2 third-generation gonadotropin assays were sufficient to diagnose central precocious puberty in >90% of the girls. Luteinizing hormone values were undetectable in both assays with different lower limits of detection (<0.15 and <0.20 U/L) in 29 of 34 prepubertal girls; the detectible values in 5 girls ranged from 0.20 to 0.66 U/L. All girls with central precocious puberty had values of >0.83 U/L, except a single value of 0.46 U/L. The basal follicle-stimulating hormone failed to differentiate prepubertal girls from those with central precocious puberty, whereas luteinizing hormone/follicle- stimulating hormone ratios would seem to have limited discernment. CONCLUSION. A single basal luteinizing hormone measurement is adequate to document a pubertal hypothalamic-pituitary-ovarian axis in most but not all girls with central precocious puberty.