The diagnosis of GH deficiency in obese patients: a reappraisal with GHRH plus arginine testing after pharmacological blockade of lipolysis.
BACKGROUND
The diagnosis of GH deficiency (GHD) in obese patients is complicated by the reduced GH secretion associated with overweight. A GH response to GHRH+arginine lower than 4.2 microg/l is currently considered indicative of GHD in obesity. The aim of the study was to investigate the effect of acute pharmacological blockade of lipolysis on the GH response to GHRH+arginine in obese patients.


METHODS
Two groups of patients were studied: 12 obese patients with proven GHD and 14 patients with essential obesity. On separate occasions, two tests were carried out in each patient: GHRH+arginine and GHRH+arginine preceded by acipimox.


RESULTS
The mean GH peak after GHRH+arginine was significantly lower in hypopituitary patients than in subjects with essential obesity. Acipimox significantly increased the mean GH response in patients with essential obesity, but not in hypopituitary subjects. All hypopituitary patients and 7/14 patients with essential obesity displayed GH peaks lower than 4.2 microg/l after GHRH+arginine: the GH response to the test increased after acipimox pretreatment in five of these seven essentially obese subjects. After acipimox administration, free fatty acids (FFAs) significantly fell in both groups with comparable mean absolute decreases. All IGF1 values were normal in both groups of subjects.


CONCLUSIONS
Our study has demonstrated that the acipimox-induced acute reduction of circulating FFA levels increases mean somatotropin response to GHRH+arginine in patients with essential obesity, whereas it has no effect in hypopituitary subjects. The current criterion for the diagnosis of GHD in obese patients may be misleading. Indeed, subjects affected by third degree obesity, like most of our patients, may be erroneously classified as really GH-deficient and started on an expensive unjustified treatment. It appears therefore that the current criteria for the diagnosis of GHD in obesity should be reconsidered in the light of further studies also taking into account different body mass index groups.
Scacchi
Massimo
M
Division of Endocrinology and Metabolic Diseases, Università degli Studi di Milano, Ospedale San Luca IRCCS, Milano, Italy.
Orsini
Federica
F
Cattaneo
Agnese
A
Grasso
Alice
A
Filippini
Barbara
B
Pecori Giraldi
Francesca
F
Fatti
Letizia Maria
LM
Moro
Mirella
M
Cavagnini
Francesco
F
D000328:Adult; D000368:Aged; D001120:Arginine; D005260:Female; D013007:Growth Hormone-Releasing Hormone; D019382:Human Growth Hormone / Q000172:deficiency*; D006801:Humans; D000960:Hypolipidemic Agents / Q000494:pharmacology; D007018:Hypopituitarism / Q000097:blood / Q000150:complications / Q000175:diagnosis*; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D016014:Linear Models; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000150:complications*; D011719:Pyrazines / Q000494:pharmacology
D000960:Hypolipidemic Agents; D007328:Insulin; D011719:Pyrazines; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D013007:Growth Hormone-Releasing Hormone; D001120:Arginine; C027696:acipimox