Prevalence of refractoriness when testing growth hormone levels in children

Objective

Late night spontaneous growth hormone (GH) pulses may influence the pituitary GH response to provocation tests. We evaluated GH response during arginine-insulin-tolerance test (AITT) after a GH peak during a short spontaneous nocturnal profile (SSNP) in children with short stature or low growth velocity.

Design

Using SSNP and subsequent AITT, we examined 257 children 4–18 years old (138 (53.7%) males) recruited from three hospitals. Medical records were reviewed retrospectively. Refractory children were defined as a GH peak ≥7 μg/L during SSNP but no GH peak ≥7 μg/L during AITT.

Results

In total, 201/257 children had a GH peak ≥7 μg/L at SSNP and/or AITT. Of these, 21.9% were refractory. The proportion of males (p = 0.033) and body mass index (BMI) standard deviation score (SDS) (p = 0.037) were higher in the refractory group than in children with a GH peak ≥7 μg/L during AITT. The median period between last GH peak ≥7 μg/L during SSNP and GH_max at AITT was 210 (30–390) minutes. The GH_max at AITT occurred 30 min earlier for children without a peak ≥7 μg/L during the SSNP (p = 0.004). The number of refractoriness differed somewhat between the hospitals (p = 0.025).

Conclusions

Many children with short stature were refractory at testing; among them we found few clinical characteristics. Refractoriness might be influenced by some differences in procedure, but needs to be considered when evaluating GH response in children.