Diagnostic utility of a low-dose gonadotropin-releasing hormone test in the context of puberty disorders.

OBJECTIVES: The 10-microg gonadotropin-releasing hormone (GnRH) test assesses pituitary gonadotroph responsiveness, whereas the 100-microg dose assesses maximal secretory capacity. Our aims were to establish normative data for the low-dose test in children and to evaluate the test in diagnosing common pubertal disorders.

METHODS: We retrospectively classified 107 children who underwent 10-microg GnRH tests into normal prepubertal (20 boys, 10 girls), normal early pubertal (10 boys, 16 girls), constitutional delay of puberty (CDP, 13 prepubertal boys >12 years), hypogonadotropic hypogonadism (HH, 5 prepubertal boys >12 years), central precocious puberty (CPP, 19 girls) or premature thelarche/variant (13 girls).

RESULTS: Peak LH response was higher in prepubertal boys >12 years compared with younger boys (p < 0.01) but showed no further change in early puberty. CDP boys had LH responses similar to prepubertal boys >12 years. HH boys showed an absent LH response which diagnosed HH with 100% sensitivity and 96% specificity. Thelarche girls had LH:FSH peak ratios lower than normal prepubertal (p = 0.001), pubertal (p < 0.05) or CPP (p = 0.001) girls.

CONCLUSIONS: We have established normative values for the low-dose GnRH test in children. The test successfully differentiated HH from CDP in boys, and contributed to the differential diagnosis of CPP and premature thelarche in girls.