Cut-off limits of the GH response to GHRH plus arginine test and IGF-I levels for the diagnosis of GH deficiency in late adolescents and young adults.
OBJECTIVE
To define the appropriate diagnostic cut-off limits for the GH response to GHRH+arginine (ARG) test and IGF-I levels, using receiver operating characteristics (ROC) curve analysis, in late adolescents and young adults.


METHODS
We studied 152 patients with childhood-onset organic hypothalamic-pituitary disease (85 males, age (mean+/-s.e.m.): 19.2+/-0.2 years) and 201 normal adolescents as controls (96 males, age: 20.7+/-0.2 years). Patients were divided into three subgroups on the basis of the number of the other pituitary hormone deficits, excluding GH deficiency (GHD): subgroup A consisted of 35 panhypopituitary patients (17 males, age: 21.2+/-0.4 years), subgroup B consisted of 18 patients with only one or with no more than two pituitary hormone deficits (7 males, age: 20.2+/-0.9 years); and subgroup C consisted of 99 patients without any known hormonal pituitary deficits (60 males, age: 18.2+/-0.2 years). Both patients and controls were lean (body mass index, BMI<25 kg/m(2)). Patients in subgroup A were assumed to be GHD, whereas in patients belonging to subgroups B and C the presence of GHD had to be verified.


RESULTS
For the GHRH+ARG test, the best pair of highest sensitivity (Se; 100%) and specificity (Sp; 97%) was found choosing a peak GH of 19.0 microg/l. For IGF-I levels, the best pair of highest Se (96.6%) and Sp (74.6%) was found using a cut-off point of 160 microg/l (SDS: -1.3). Assuming 19.0 microg/l to be the cut-off point established for GHRH+ARG test, 72.2% of patients in subgroup B and 39.4% in subgroup C were defined as GHD. In patients belonging to group B and C and with a peak GH response <19 microg/l to the test, IGF-I levels were lower than 160 microg/l (or less than 1.3 SDS) in 68.7 and 41.6% of patients respectively predicting severe GHD in 85.7% of panhypopituitary patients (subgroup A).


CONCLUSIONS
In late adolescent and early adulthood patients, a GH cut-off limit using the GHRH+ARG test lower than 19.0 microg/l is able to discriminate patients with a suspicion of GHD and does not vary from infancy to early adulthood.
Endocrinology, Department of Clinical and Experimental Medicine, Amedeo Avogadro University of Novara, Via Solaroli, 17, 28100 Novara, Italy.
Ginevra
G
Corneli
Carolina
C
Di Somma
Flavia
F
Prodam
Jaele
J
Bellone
Simonetta
S
Bellone
Valentina
V
Gasco
Roberto
R
Baldelli
Silvia
S
Rovere
Harald Jörn
HJ
Schneider
Luigi
L
Gargantini
Roberto
R
Gastaldi
Lucia
L
Ghizzoni
Domenico
D
Valle
Mariacarolina
M
Salerno
Annamaria
A
Colao
Gianni
G
Bona
Ezio
E
Ghigo
Mohamad
M
Maghnie
Gianluca
G
Aimaretti
D000293:Adolescent; D000328:Adult; D001120:Arginine; D005260:Female; D013007:Growth Hormone-Releasing Hormone; D019382:Human Growth Hormone / Q000172:deficiency* / Q000378:metabolism*; D006801:Humans; D007018:Hypopituitarism / Q000175:diagnosis*; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D012372:ROC Curve; D012680:Sensitivity and Specificity
D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D013007:Growth Hormone-Releasing Hormone; D001120:Arginine