[Hypogonadotropic hypogonadism and delayed puberty: differential diagnosis using the LH-RH-infusion test]

Serum concentrations of LH and FSH were determined during an intravenous infusion of LH-RH (200 micrograms, t = 4 hours) in 8 patients (age: 15 to 20 years) with delayed sexual maturation and retarded bone age. Four patients who by clinical criteria were later recognized as suffering from hypogonadotropic hypogonadism (HH) presented during the infusion of LH-RH with only a small response of LH (and, in three cases, of FSH). In 3 patients with HH a deficiency of endogenous LH-RH due to a hypothalamic defect was suggested by an enhanced secretion of LH and FSH during a second LH-RH infusion test performed after priming of the pituitary by pulsatile, subcutaneous infusions of LH-RH (50 micrograms/night for 9 consecutive nights). The fourth patient with HH, who suffered from a pituitary adenoma, failed to display this enhanced secretion of gonadotropins following pituitary priming by intermittent administration of LH-RH. As compared with the patients with HH, 4 patients in whom puberty, although delayed, later occurred spontaneously (pubertas tarda, PT), presented with a considerably more pronounced secretion of LH and FSH during the infusion of LH-RH, and priming by intermittent subcutaneous LH-RH failed to achieve further enhancement of the secretion of LH and FSH during a second infusion test in these patients. The intravenous infusion of LH-RH in combination with a protocol of pituitary priming offers a possibility of distinguishing patients with delayed puberty from those with various forms of hypogonadotropic hypogonadism.