What is a normal stimulated growth hormone concentration?

Area of Science:

• Pediatric Endocrinology
• Growth Hormone Disorders
• Diagnostic Testing

Background:

• Short stature in children necessitates accurate diagnosis of growth hormone (GH) insufficiency.
• The insulin tolerance test (ITT) is a common method to assess GH secretion.
• Establishing reliable diagnostic criteria is crucial for timely intervention.

Purpose of the Study:

• To determine optimal "cut-off" values for serum GH concentration following ITT in short prepubertal children.
• To correlate GH response to ITT with individual growth rates (height velocity SDS).
• To evaluate the efficiency, sensitivity, and specificity of the ITT for diagnosing GH insufficiency.

Main Methods:

• Retrospective analysis of 148 short prepubertal children (aged 3.9-11.9 years).
• Comparison of serum GH concentration response to ITT with height velocity standard deviation scores (SDS).
• Calculation of diagnostic performance metrics (efficiency, sensitivity, specificity) at various GH cut-off levels.

Main Results:

• Children with height velocity SDS > -0.8 (Group 1) had significantly higher median peak GH responses (19.9 mU/l) than Group 2 (SDS < -0.8, 9.9 mU/l).
• A cut-off value of 13.5 mU/l in the Hybritech assay yielded optimal efficiency (66%), sensitivity (64%), and specificity (70%).
• The relationship between GH response and growth rate was continuous, not discrete.

Conclusions:

• A serum GH cut-off of 13.5 mU/l demonstrated good diagnostic utility in this cohort.
• Individual laboratories should establish their own "normal" cut-off values based on their specific GH assay.
• The study highlights the continuous nature of GH response in relation to growth velocity.