Relationship between GH response and glycemic fluctuations in the glucagon stimulation test.
OBJECTIVE
Verifying the association between glycemic fluctuation and GH response in the glucagon stimulation test. Basal evaluation of growth hormone (GH) has poor diagnostic accuracy due to its pulsatile secretion. GH-stimulation tests are used for an adequate evaluation of somatotrophic axis. Various stimuli can be employed, among them glucagon, which has an elusive mechanism of action. Since hypoglycemia reportedly occurs during the test, investigation of its role as a stimulus to GH release is granted.


METHODS
Retrospective analysis of glucagon-stimulated GH tests performed in 128 children (36.7% female; age 12.4+3.3 years), at Fleury Functional Tests Facility from July 2000 to 2006. GH and blood glucose (BG) curves, IGF-1, and IGFBP-3 have been assessed. Positive GH response was defined by a peak GH value >or=3.3 microg/L. Normal IGF-1 levels were defined as those between 2.5th and 97.5th percentiles for age and gender.


RESULTS
Hypoglycemia under 2.2 mmol/L did not occur during the test. BG decrease occurred with lower magnitude and was not associated to GH response. Comparison between patients with negative and positive GH response showed, respectively, BG nadir 3.74 vs. 3.62 mmol/L, glucose AUC 23.3 vs. 22.4, and glycemic decrease (below 3.3 mmol/L) 19% vs. 35.5% (with P non-significant for all comparisons).


CONCLUSIONS
Hypoglycemia was not seen after glucagon stimulation and decrease in BG occurred above levels physiologically expected to stimulate GH release, being apparently not associated to GH response.
Giuffrida
Fernando M A
FM
Fleury Medicina e Saúde-Setor de Provas Funcionais, São Paulo-SP, Brazil. fernandogiuffrida@uol.com.br
Berger
Karina
K
Monte
Lia
L
Oliveira
Claudia H M C
CH
Hoff
Ana O
AO
Maciel
Rui M B
RM
Vieira
José Gilberto H
JG
D000293:Adolescent; D001786:Blood Glucose / Q000378:metabolism*; D002648:Child; D005260:Female; D005934:Glucagon; D019382:Human Growth Hormone / Q000378:metabolism*; D006801:Humans; D007003:Hypoglycemia / Q000378:metabolism*; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D012189:Retrospective Studies
D001786:Blood Glucose; C515497:IGFBP3 protein, human; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D005934:Glucagon