Pegvisomant-primed growth hormone (GH) stimulation test is useful in identifying true GH deficient children.

Objective: Provocative stimulation tests for growth hormone (GH) assessment have poor reproducibility and can often elicit false positive results in normal children. The aim of our study was to confirm the capability of pegvisomant as an enhancer of GH secretion in unmasking false-positive results in short children (height <-2.0 standard deviation score, SDS) undergoing GH testing.

Design: A prospective study was conducted between March and August 2016. Twenty short children (10 males and 10 females), aged 4.6-13.4 years, previously diagnosed as GH deficient (GHD) were included in the study. All subjects received 1 mg/kg of pegvisomant subcutaneously; three days later an insulin tolerance test (ITT) was performed. Insulin-like growth factor-I (IGF-I) was evaluated before and three days after pegvisomant administration.

Results: After pegvisomant priming and the ITT stimulation test, 12 out of the 20 children initially classified as GHD showed a GH peak of more than 10 ng/ml and were thus reclassified as short normal. Furthermore, a significant reduction of IGF-I was observed in the GHD group (pre IGF-I: median (IQR) 144.0 (109-248) ng/ml, post IGF-I: 98 (49-165) ng/ml; p<0.001) after pegvisomant administration.

Conclusions: Pegvisomant priming before GH stimulation tests can be used to improve the reliability of the diagnostic work-up in GH deficiency.