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.
Corneli
Ginevra
G
Endocrinology, Department of Clinical and Experimental Medicine, Amedeo Avogadro University of Novara, Via Solaroli, 17, 28100 Novara, Italy.
Di Somma
Carolina
C
Prodam
Flavia
F
Bellone
Jaele
J
Bellone
Simonetta
S
Gasco
Valentina
V
Baldelli
Roberto
R
Rovere
Silvia
S
Schneider
Harald Jörn
HJ
Gargantini
Luigi
L
Gastaldi
Roberto
R
Ghizzoni
Lucia
L
Valle
Domenico
D
Salerno
Mariacarolina
M
Colao
Annamaria
A
Bona
Gianni
G
Ghigo
Ezio
E
Maghnie
Mohamad
M
Aimaretti
Gianluca
G
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