Related Experiment Video
Updated: Sep 26, 2026
Functional Interrogation of Adult Hypothalamic Neurogenesis with Focal Radiological Inhibition
Published on: November 14, 2013
GH values after clonidine stimulation measured by immunofluorometric assay in normal prepubertal children and
Eveline G P Silva1, Natasha Slhessarenko, Ivo J P Arnhold
1Unidade 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.
Insights
This study establishes new cut-off values for growth hormone (GH) using a sensitive immunofluorometric assay in children. A 3.3 micro g/l threshold aids in accurately diagnosing GH deficiency.
Area of Science:
- Pediatric Endocrinology
- Biochemical Assays
- Growth Hormone Research
Background:
- Growth hormone (GH) deficiency diagnosis relies on accurate measurement of GH levels.
- Traditional assays may lack the sensitivity and specificity required for precise diagnosis.
- Establishing reliable cut-off values is crucial for differentiating normal GH secretion from deficiency.
Purpose of the Study:
- To determine reference cut-off values for GH in normal prepubertal children using an immunofluorometric assay (IFA).
- To compare these IFA-derived values with those from patients diagnosed with GH deficiency.
- To validate the utility of IFA for diagnosing GH deficiency in pediatric populations.
Main Methods:
- A clonidine stimulation test was administered to 30 normal prepubertal children and 26 patients with known GH deficiency.
- Blood samples were collected at multiple time points (-30, 0, 60, 90, 120 minutes) post-administration.
- GH levels were quantified using a sensitive immunofluorometric assay.
Main Results:
- Normal children exhibited a wide range of peak GH values (1.7–25 micro g/l).
- The 5th and 10th percentile cut-off values were determined to be 3.3 and 5.5 micro g/l, respectively.
- GH-deficient patients showed significantly lower peak GH levels (<0.1–2.1 micro g/l).
Conclusions:
- The immunofluorometric assay yields lower GH cut-off values compared to radioimmunoassay.
- A suggested cut-off value of 3.3 micro g/l (5th percentile) demonstrates 100% sensitivity and 93% specificity.
- This IFA-based cut-off value facilitates reliable exclusion of GH deficiency in children.
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.
