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Growth hormone response to oral clonidine test in normal and short children
Insights
Height velocity (HV) helps predict growth hormone (GH) response in children. Short children with subnormal HV are more likely to have a GH deficiency, guiding diagnostic accuracy for GH testing.
Area of Science:
- Pediatric Endocrinology
- Growth Hormone Physiology
- Diagnostic Testing
Background:
- Growth hormone (GH) deficiency is a significant cause of short stature in children.
- Accurate diagnosis relies on dynamic testing, but interpretation can be challenging.
- Height velocity (HV) is a key indicator of growth patterns.
Purpose of the Study:
- To evaluate the diagnostic utility of the clonidine stimulation test for growth hormone assessment.
- To determine if height velocity (HV) can predict the growth hormone (GH) response to clonidine.
- To assess the sensitivity and specificity of the clonidine test in identifying children with suspected GH deficiency.
Main Methods:
- A clonidine stimulation test was administered to three groups of prepubertal children: normal stature, short stature with normal HV, and short stature with subnormal HV.
- Peak GH levels were measured after clonidine administration.
- Sensitivity and specificity were calculated using a cutoff of 10 micrograms/l for GH response.
Main Results:
- Mean peak GH levels after clonidine were similar across all three groups.
- The clonidine test showed 50% sensitivity and 83% specificity for identifying children with suspected GH deficiency (short stature with subnormal HV).
- Height velocity was a useful predictor, as most children with normal growth rates exhibited normal GH responses.
Conclusions:
- Height velocity is a valuable parameter for predicting GH response to stimulation tests.
- The clonidine test's diagnostic accuracy is moderate, especially in differentiating true GH deficiency.
- Further investigation may be needed for children with borderline GH responses and subnormal HV.
Abstract:
We evaluated the growth hormone (GH) response to an acute clonidine test (0.15 mg/m2 po) in 30 normal prepubertal children (stature between the 3rd and 97th centile), in 29 short children (stature < 3rd centile for age) with height velocity (HV) > 10th centile and in 20 short children with HV < 10th centile. The three groups had comparable chronological ages. After clonidine administration mean peak GH levels were similar in the three groups (19.4 +/- 9.8, 17.7 +/- 8.8 and 14.6 +/- 8.9 micrograms/l, mean +/- SD, respectively). By choosing 10 micrograms/l as the limit for a normal response we found that stimulated GH levels had a sensitivity of 50% and a specificity of 83% in identifying children with suspected GHD (short children with subnormal HV). The diagnostic accuracy was almost superimposable, for cut-off values of 10 and 12 micrograms/l. Eight of the 10 children with subnormal HV and a GH peak < 10 micrograms/l had a GH peak < 10 micrograms/l also after a second stimulation test. Six of the 29 short children with normal HV had a GH peak < 10 micrograms/l. Only one of them had a GH peak < 10 micrograms/l after a second stimulation test. Five of the normal children had peak GH levels < 10 micrograms/l. These results indicate that HV is a useful variable to predict the GH response to an acute GH stimulus, since the great majority of children with a normal growth rate had a normal GH response to at least one stimulation test.