GH values after clonidine stimulation measured by immunofluorometric assay in normal prepubertal children and GH-deficient patients.
OBJECTIVE
To establish the cut-off values of GH measured by immunofluorometric assay, a more sensitive and specific assay, in normal prepubertal children and compare their values with those of proven GH-deficient patients.


METHODS
30 normal children (20 males) and 26 patients with known causes of GH deficiency were submitted to the clonidine test and their GH values were compared. A powdered clonidine tablet (0.1 mg/m(2)) was given orally and blood samples for GH measurements were drawn at times -30, 0, 60, 90 and 120 min.


RESULTS
GH peak values presented a wide variation ranging from 1.7 to 25 micro g/l (mean +/- SD = 12.87 +/- 5.8 micro g/l) in the normal group. The cut-off values for the 5th and 10th percentiles of the distribution curve were 3.3 and 5.5 micro g/l, respectively. In the GH deficiency group, maximum GH levels after clonidine stimulation ranged from <0.1 to 2.1 micro g/l (0.56 +/- 0.58 micro g/l).


CONCLUSIONS
The cut-off values obtained with the immunofluorometric method are lower than the ones obtained by radioimmunoassay. We suggest a cut-off value of 3.3 micro g/l (5th percentile) that ensures 100% of sensitivity along with 93% of specificity to exclude the diagnosis of GH deficiency when using this immunofluorometric method.
Silva
Eveline G P
EG
Unidade de Endocrinologia do Desenvolvimento e Laboratório de Hormônios e Genética Molecular LIM /42, Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Brazil.
Slhessarenko
Natasha
N
Arnhold
Ivo J P
IJ
Batista
Marcelo C
MC
Estefan
Vivian
V
Osorio
Maria G F
MG
Marui
Suemi
S
Mendonca
Berenice B
BB
D000293:Adolescent; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003000:Clonidine / Q000494:pharmacology*; D005260:Female; D019085:Fluorescent Antibody Technique, Direct; D019382:Human Growth Hormone / Q000097:blood / Q000172:deficiency* / Q000187:drug effects*; D006801:Humans; D007223:Infant; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D036341:Intercellular Signaling Peptides and Proteins / Q000097:blood; D008297:Male; D012016:Reference Values
D000316:Adrenergic alpha-Agonists; D018972:Insulin-Like Growth Factor Binding Protein 3; D036341:Intercellular Signaling Peptides and Proteins; C065700:myotrophin; D019382:Human Growth Hormone; D003000:Clonidine