Diagnosis of growth hormone deficiency after pituitary surgery: the combined acipimox/GH-releasing hormone test.
OBJECTIVE
Reduction of plasma free fatty acids leads to enhanced GH response after stimulation by GH-releasing hormone (GHRH). We studied the clinical usefulness of combined administration of acipimox and GHRH for the diagnosis of GH deficiency.


METHODS
We evaluated 35 patients [mean age 53.0 years; mean body mass index (BMI) 26.7 kg/m2] after pituitary surgery. We compared GH responses after acipimox and GHRH with the GH response during an insulin tolerance test (ITT) and, in a subgroup of 12 patients, with the GHRH/arginine test. The acipimox/GHRH test was additionally performed in 21 control subjects (mean age 53.8 years; mean BMI 24.7 kg/m2).


RESULTS
In the patients, the mean (+/- SEM) peak GH was almost four-fold higher after acipimox/GHRH (6.94 +/- 1.07 microg/l, range 0.46-23.1; P < 0.001) and after GHRH/arginine (8.32 +/- 1.23 microg/l, range 1.1-49.2; P < 0.001) than after ITT (1.84 +/- 0.46 microg/l, range 0.01-11.9). According to the ITT, 29 patients were severely GH deficient (peak GH < 3.0 microg/l). Peak GH levels after acipimox/GHRH in controls ranged from 7.5 to 78.4 microg/l (mean 29.3 +/- 3.5). GH peak values during the acipimox/GHRH test were significantly correlated with values from the ITT (r = 0.63, P < 0.01) and GHRH/arginine test (r = 0.87, P < 0.001). Areas under the curve were also correlated. According to generally accepted cut-off peak GH levels for the ITT and GHRH/arginine test, a GH peak exceeding 11.2 micro g/l excludes severe GH deficiency after acipimox/GHRH. Our control data indicate that the cut-off level is lower at older age.


CONCLUSIONS
The acipimox/GHRH test leads to GH responses similar to those of the GHRH/arginine test, and to higher peak GH values if compared with the ITT. The acipimox/GHRH test is a potential additional tool to detect GH deficiency in patients with pituitary disease, in particular in patients with a perturbation of fatty acid metabolism.
van Dam
P Sytze
PS
Department of Clinical Endocrinology, University Medical Center, Utrecht, the Netherlands. p.s.vandam@digd.azu.nl
Dieguez
Carlos
C
Cordido
Fernando
F
de Vries
Wouter R
WR
Veldhuyzen
Bernard F E
BF
van Thiel
E
E
Casanueva
Felipe F
FF
Koppeschaar
Hans P F
HP
D000236:Adenoma / Q000097:blood / Q000601:surgery*; D000293:Adolescent; D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001120:Arginine; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D013006:Growth Hormone / Q000097:blood / Q000172:deficiency*; D013007:Growth Hormone-Releasing Hormone; D006801:Humans; D007328:Insulin; D008297:Male; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000097:blood / Q000601:surgery*; D011237:Predictive Value of Tests; D011719:Pyrazines; D013268:Stimulation, Chemical
D005230:Fatty Acids, Nonesterified; D007328:Insulin; D011719:Pyrazines; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D001120:Arginine; C027696:acipimox