GnRH Stimulation Test
In case of delayed or premature puberty. Further diagnostic work-up in hypogonadotropic hypogonadism: the GnRH test distinguishes between hypothalamic (tertiary) or hypophyseal (secondary) hypogonadism.
Measurement of LH and FSH in serum before administration of 100 μg GnRH i.v. (for children 60 μg per m2 BSA, maximum 100 μg GnRH), after 30 min LH and FSH are measured again.
Normal values in puberty:
Basal LH <2 U/l, FSH <2 U/l, after stimulation LH rises >5 U/l, FSH rises too but to a smaller extent compared to LH. The extent of LH surge correlates with maturity during puberty.
Interpretation in hypogonadotropic hypogonadism:
LH should increase to 2–4 fold, FSH to 1.5–2 fold. The regular increase excludes a pituitary cause and suggests a hypothalamic disease (Kallmann syndrome).
Interpretation in precocious puberty:
Low basal concentrations of LH and FSH without a significant increase after stimulation suggest peripheral hormone production (especially gonadotropin-independent tumors). Central precocious puberty is characterized by elevated basal gonadotropins, which increase disproportionately after stimulation.
Index: 1–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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