Spontaneous serum gonadotropin concentrations in the evaluation of precocious puberty.

OBJECTIVE

We assessed the utility of spontaneous and gonadotropin-releasing hormone (GnRH)-stimulated serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels measured by new immunochemiluminometric assays in the evaluation and monitoring of precocious puberty.

METHODS

We evaluated serum gonadotropin values from intravenous GnRH stimulation tests in 49 girls with clinical signs suggesting central precocious puberty (CPP). Because GnRH-stimulated LH has been considered the standard for diagnosing CPP, we used it as the basis for comparison with GnRH-stimulated FSH levels and spontaneous LH and FSH measured by immunochemiluminometric assay.

RESULTS

Twenty-six patients had a peak serum LH value above the +2 SD threshold for normal prepubertal female subjects (LH > 5 IU/L). The GnRH-stimulated FSH values had a narrow range and did not discriminate patients with CPP. In contrast, elevations in spontaneous LH and FSH were found to be specific for CPP. Spontaneous LH levels correlated strongly with peak stimulated LH levels in subjects with precocious puberty (r = 0.79) or in control subjects (r = 0.93, both p (0.0001). Spontaneous LH levels in excess of 0.1 IU/L detected true puberty with 94% sensitivity and 88% specificity. Random LH levels in excess of 0.3 IU/L had 100% specificity for CPP.

CONCLUSIONS

The GnRH-stimulated FSH levels do not adequately differentiate children with and without CPP and have limited utility in the evaluation of precocious puberty. Spontaneous FSH levels are elevated in CPP with fair sensitivity and marked specificity. Elevated random LH, measured by third-generation assay such as immunochemiluminometric assay, is strongly correlated with and highly predictive of elevated peak GnRH-stimulated LH, and is a useful screening tool for CPP.