Acylated ghrelin as a provocative test for the diagnosis of GH deficiency in adults.
OBJECTIVE
Insulin tolerance test (ITT) is the test of reference for the diagnosis of adult GH deficiency (GHD), although GHRH in combination with arginine (ARG) or GH secretagogues are considered equally reliable tests. Testing with GH secretagogue alone is, anyway, a potent stimulus exploring the integrity of hypothalamic pathways controlling somatotropic function. We therefore aimed to determine the diagnostic reliability of testing with ghrelin, the natural GH secretagogue.


METHODS
We studied the GH response (every 15 MIN from 15 TO +120 MIN) to acylated ghrelin (1G/KG I.V. AT 0MIN) IN 78 patients with a history of pituitary disease (49 male, 29 female; age (MEANS.D.): 52.1±18.7 years; BMI: 26.7±5.3 kg/m(2)). The lack of GH response to GHRH+ARG and/or ITT was considered the gold standard for the diagnosis of GHD. The best GH cut-off to ghrelin test, defined as the one with the best sensitivity (SE) and specificity (SP), was identified using the receiver-operating characteristic curve analysis.


RESULTS
The best GH cut-off to ghrelin test was 7.3 μg/l in lean subjects (SE 88.2%, SP 90.9%), 2.9 μg/l in overweight subjects (SE 92.6%, SP 100%) and 0.6 μg/l in obese subjects (SE 50%, SP 100%). The diagnostic accuracy was 89.3, 94.1 and 62.5% respectively.


CONCLUSIONS
Our data show that testing with acylated ghrelin represents a reliable diagnostic tool for the diagnosis of adult GHD, in lean and overweight subjects, if appropriate cut-off limits are assumed. Obesity strongly reduces GH response to ghrelin, GH weight-related cut-off limit and diagnostic reliability of the test.
Department of Medical Science, University of Turin, Turin, Italy.
Valentina
V
Gasco
Guglielmo
G
Beccuti
Chiara
C
Baldini
Nunzia
N
Prencipe
Stellina
S
Di Giacomo
Alessandro
A
Berton
Federica
F
Guaraldi
Isabella
I
Tabaro
Mauro
M
Maccario
Ezio
E
Ghigo
Silvia
S
Grottoli
D000328:Adult; D001120:Arginine; D005260:Female; D054439:Ghrelin; D013007:Growth Hormone-Releasing Hormone; D019382:Human Growth Hormone / Q000172:deficiency / Q000378:metabolism*; D006801:Humans; D007018:Hypopituitarism / Q000175:diagnosis*; D007328:Insulin; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012680:Sensitivity and Specificity
D054439:Ghrelin; D007328:Insulin; D019382:Human Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D001120:Arginine