Basal follicle-stimulating hormone and peak gonadotropin levels after gonadotropin-releasing hormone infusion show high diagnostic accuracy in boys with suspicion of hypogonadotropic hypogonadism.
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.
Grinspon
Romina P
RP
Centro de Investigaciones Endocrinológicas, División de Endocrinología, Hospital de Niños R. Gutiérrez, Gallo 1330, C1425EFD Buenos Aires, Argentina.
Ropelato
María Gabriela
MG
Gottlieb
Silvia
S
Keselman
Ana
A
Martínez
Alicia
A
Ballerini
María Gabriela
MG
Domené
Horacio M
HM
Rey
Rodolfo A
RA
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
D006062:Gonadotropins; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone