A simplified gonadotrophin-releasing hormone test for precocious puberty.

BACKGROUND AND OBJECTIVE: The gonadotrophin-releasing hormone (GnRH) test is important for the evaluation of children with disorders of puberty. Traditionally, the test determines the peak LH and the peak FSH responses from 5 to 8 blood samples, which makes it cumbersome and costly. We suspected that the test could be simplified to require fewer hormonal measurements.

DESIGN: A retrospective clinical study.

PATIENTS: Subjects were 44 girls and 7 boys with signs of precocious puberty, of whom 39 were diagnosed as definite central precocious puberty. Fifty-five diagnostic tests and 39 tests for suppression during GnRH-analogue treatment were reviewed.

MEASUREMENTS: LH and FSH were measured in serum samples obtained during a standard GnRH test.

PARAMETERS: LH and FSH responses and the LH:FSH ratio at 30, 45 and 60 minutes, and the respective peak levels. For each parameter, the sensitivities and specificities were estimated and the receiver operating characteristic curve was constructed.

RESULTS: The receiver operating characteristic curves for the LH responses at 30, 45 and 60 minutes and peak, were similar and showed high specificities and sensitivities for the diagnosis of central precocious puberty. A single LH cut-off (15 IU/I) had diagnostic sensitivity > 90% and specificity > 80% for LH concentrations at 30, 45 or 60 minutes and peak, and sensitivity > 90% to detect suppression. Calculations of the LH:FSH ratio did not improve the diagnostic accuracy of the GnRH test achieved by LH alone.

CONCLUSIONS: A single LH determination 30 minutes after GnRH administration is as useful as the peak LH; FSH measurements are unnecessary for the differential diagnosis of central precocious puberty. We propose that for the diagnosis of central precocious puberty and for treatment monitoring, the GnRH test to be simplified to LH measurement in a single blood sample at 30 minutes.