Usefulness and limits of GnRH test in boys with lack of sexual maturation

In 39 boys between 14 and 22.6 years of age with lack of sexual maturation, the response of the serum gonadotrophins to a single intravenous administration of GnRH was studied and the clinical evolution was followed. In 30 patients LH secretion after GnRH showed a pubertal pattern. Subsequently they all had spontaneous puberty. In 9 patients, the LH response to GnRH was prepubertal. Four of them subsequently showed spontaneous pubertal maturation. In the 5 others, testicular size remained prepubertal, suggesting the diagnosis of isolated gonadotrophin deficiency. Thus 34/39 patients had constitutionally delayed puberty. In 30 of the former biological evidence of hypothalamopituitary maturation precede the appearance of physical puberty. Consequently, normal LH response reassures the patients and their family as to the prognosis. If prepubertal in pattern, the gonadotrophin response to GnRH should be interpreted cautiously and the evolution awaited.