title: Basal follicle-stimulating hormone and peak gonadotropin levels after gonadotropin-releasing hormone infusion show high diagnostic accuracy in boys with suspicion of hypogonadotropic hypogonadism.
abstract: BACKGROUND
  Differential diagnosis between hypogonadotropic hypogonadism (HH) and constitutional delay of puberty in boys is challenging. Most tests use an acute GnRH stimulus, allowing only the release of previously synthesized gonadotropins. A constant GnRH infusion, inducing de novo gonadotropin synthesis, may allow a better discrimination.
  
  
  OBJECTIVE
  We evaluated the diagnostic accuracy of basal and peak gonadotropins after GnRH infusion, measured by ultrasensitive assays, to confirm the diagnosis in boys with suspected HH.
  
  
  METHODS
  We conducted a validation study following Standards for Reporting of Diagnostic Accuracy criteria at a tertiary public hospital.
  
  
  METHODS
  A GnRH i.v. infusion test was performed in 32 boys. LH and FSH were determined by immunofluorometric assay at 0-120 min. DIAGNOSIS ASCERTAINMENT: The following diagnoses were ascertained: complete HH (n = 19; testes < 4 ml at 18 yr), partial HH (n = 6; testes enlargement remained arrested for > or = 1 yr or did not reach 15 ml), and constitutional delay of puberty (n = 7; testes > or = 15 ml at 18 yr).
  
  
  METHODS
  Sensitivity, specificity, positive and negative predictive values, and diagnostic efficiency were assessed.
  
  
  RESULTS
  Basal FSH less than 1.2 IU/liter confirmed HH with specificity of 1.00 (95% confidence interval = 0.59-1.00), rendering GnRH infusion unnecessary. In patients with basal FSH of at least 1.2 IU/liter, the coexistence of peak FSH less than 4.6 IU/liter and peak LH less than 5.8 IU/liter after GnRH infusion had high specificity (1.00; 95% confidence interval = 0.59-1.00) and diagnostic efficiency (76.9%) for HH.
  
  
  CONCLUSIONS
  Basal FSH less than 1.2 IU/liter confirms HH, which precludes from further testing, reducing patient discomfort and healthcare system costs. In patients with basal FSH of at least 1.2 IU/liter, a GnRH infusion test has a high diagnostic efficiency.
authors.affiliation: Centro de Investigaciones Endocrinológicas, División de Endocrinología, Hospital de Niños R. Gutiérrez, Gallo 1330, C1425EFD Buenos Aires, Argentina.
authors.forename: Romina P
authors.initials: RP
authors.lastname: Grinspon
authors.forename: María Gabriela
authors.initials: MG
authors.lastname: Ropelato
authors.forename: Silvia
authors.initials: S
authors.lastname: Gottlieb
authors.forename: Ana
authors.initials: A
authors.lastname: Keselman
authors.forename: Alicia
authors.initials: A
authors.lastname: Martínez
authors.forename: María Gabriela
authors.initials: MG
authors.lastname: Ballerini
authors.forename: Horacio M
authors.initials: HM
authors.lastname: Domené
authors.forename: Rodolfo A
authors.initials: RA
authors.lastname: Rey
mesh_terms: D000293:Adolescent; D003937:Diagnosis, Differential; D005470:Fluorometry; D005640:Follicle Stimulating Hormone / Q000097:blood*; D007987:Gonadotropin-Releasing Hormone; D006062:Gonadotropins / Q000097:blood* / Q000172:deficiency*; D006801:Humans; D007006:Hypogonadism / Q000097:blood* / Q000175:diagnosis*; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D011237:Predictive Value of Tests; D011628:Puberty, Delayed / Q000175:diagnosis / Q000209:etiology; D012015:Reference Standards; D015203:Reproducibility of Results; D012189:Retrospective Studies
chemical_list: D006062:Gonadotropins; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone