Growth hormone release after glucagon as a reliable test of growth hormone assessment in adults.
OBJECTIVE
To investigate the GH response to glucagon in adult patients with GH deficiency and in controls compared with the GH response to the insulin tolerance test (ITT) in patients with GH deficiency and to determine whether the use of glucagon results in a diagnostic utility test.


METHODS
Seventy-three patients with adult GH deficiency and organic hypothalamic-pituitary disease were recruited, along with 46 controls. The patients were divided into five groups according to the number of associated hormone deficiencies present.


METHODS
Hypopituitary subjects underwent assessment of GH secretory status by the ITT, the glucagon test and measurement of serum IGF-I concentration. Controls underwent the glucagon test. After the ITT, glucose and GH levels were measured at baseline, 30, 60 and 90 minutes, and after glucagon at baseline, 90, 120, 150, 180, 210 and 240 minutes.


RESULTS
The highest GH value after the ITT in the patient group was 3 microg/l (0.76 +/- 0.82 microg/l), and after the glucagon test the highest GH peak value was 2.9 microg/l (0.64 +/- 0.79 microg/l). A correlation was found between the GH peak and the progressive number of hormone deficiencies. After the glucagon test, the GH peak obtained in the controls at 180 minutes was 9.8 +/- 4.6 microg/l and, on an individual basis, none of the 46 controls failed to achieve peak GH levels higher than 3 microg/l. In the controls, a negative correlation was observed between the GH response to glucagon and age (r = -0.389, P = 0.0075) and body mass index (r = -0.329, P = 0.0254). The accuracy of the glucagon test for differentiating patients from controls, estimated by receiver operating characteristics (ROC) curve methodology, showed that the cut-off of 3 microg/l for the GH peak provides 100% sensitivity and 100% specificity and is a reliable decision threshold.


CONCLUSIONS
The glucagon GH test is reliable and provides a clear separation between GH-deficient and normal adults. A single glucagon test with a cut-off of 3 microg/l for the GH peak is diagnostic of GH deficiency in adults and could be considered and studied as an alternative to the ITT.
Gómez
José Manuel
JM
Endocrine Unit, Hospital Prínceps d'Espanya, Spain. jmgs@csub.scs.es
Espadero
Rosa María
RM
Escobar-Jiménez
Fernando
F
Hawkins
Federico
F
Picó
Antonio
A
Herrera-Pombo
José Luis
JL
Vilardell
Enric
E
Durán
Alejandra
A
Mesa
Jordi
J
Faure
Eduardo
E
Sanmartí
Anna
A
D000293:Adolescent; D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D005260:Female; D005934:Glucagon; D019382:Human Growth Hormone / Q000172:deficiency* / Q000378:metabolism; D006801:Humans; D007328:Insulin; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012680:Sensitivity and Specificity
D001786:Blood Glucose; D007328:Insulin; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D005934:Glucagon