PLACE OF GONADOTROPIN-RELEASING-HORMONE ( GNRH) TEST IN THE DIFFERENTIAL-DIAGNOSIS OF DELAYED PUBERTY IN ADOLESCENTS AGED MORE THAN 14 YEARS

In patients with delayed puberty with a bone age less than 11 years in girls or 12 years in boys, the clinical and endocrinological examinat ion allows the differentiation of patients with the various forms of h ypergonadotropic hypogonadism, but not of patients with hypogonadotrop ic hypogonadism from more prevalent constitutional delay in puberty. T herefore, watchful waiting is generally recommended for differential d iagnosis in patients with delayed puberty. On the other hand, the late onset of sexual hormone replacement in patients with hypogonadism wil l worsen their outcome. Patients and Method: Therefore, we decided to carry out a retrospective study in 105 adolescents who were examined b ecause of short stature or delayed puberty, who were aged 14 to 22 yea rs at first visit and in whom the differential diagnosis of delayed pu berty was documented after an at least one-year follow-up in order to find out which endocrinological parameters could have effectively pred icted the final diagnosis already at the first visit. Results: Patient s with hypogonadotropic hypogonadism differed from patients with const itutional delay in puberty by lower responses of luteinizing hormone ( LH) and follicle-stimulating hormone (FSH) levels to gonadotropin-rele asing hormone stimulation (GnRH, 100 mug iv) (p < 0.01) as well as by smaller testicular volume (p < 0.05) and by lower testosterone levels (p < 0.01). Stimulated LH < 10 mU/ml differentiated patients with hypo gonadotropic hypogonadism from constitutional delay in puberty with a sensitivity of 82% and a specificity of 98%. Conclusion: In patients w ith delayed puberty aged 14 years and older bone age usually exceeds 1 1 years in girls or 12 years in boys. It thus is in the range, in whic h normal adult responses of LH to GnRH can be expected. In contrast to patients aged less than 14 years, therefore, measuring GnRH-stimulate d LH levels in these patients allows the rapid and effective different ial diagnosis of delayed puberty.