Endocrine Abstracts

Background: The diagnosis of isolated GH deficiency (IGHD) is based on multiple factors: clinical, radiological and biochemical along with suboptimal peak GH levels demonstrated on dynamic testing. Recent guidance from the National Institute of Clinical Excellence (NICE; UK; 2010) advises that two GH stimulation tests must demonstrate a subnormal GH peak <6.7 μg/l (20 mU/l) to confirm the diagnosis of IGHD. In our centre, three different GH provocation tests are used: insulin tolerance, glucagon stimulation (1st line) and arginine stimulation (2nd line).

Objective and hypotheses: To see if other clinical and biochemical parameters can increase the sensitivity of GH provocation testing for the diagnosis of IGHD.

Methods: A retrospective case-review of all patients in a single centre from 2002 to 2012 undergoing two provocation tests, comparing those with two abnormal GH test results vs those with one abnormal result.

Results: 107 children had two GH provocation tests; 41% with an abnormal 1st test had a normal GH response on retesting. Lowering the cut-off to 2.7 μg/l (~8 mU/l), missed 50% of children who would have otherwise met NICE GHD criteria. In patients who failed both tests, 35.3% had a low IGF1 and 30.0% had a delayed bone age (BA) >2 years vs 26.5% with low IGF1 and 20.5% with delayed BA in patients passing the 2nd test (P 0.44 and 0.45 respectively).

Conclusions: Many children failing a 1st GH stimulation test will have a normal GH peak on re-test with no absolute cutoff peak on the 1st test that predicts an abnormal 2nd test. Moreover, a significantly delayed bone age or low IGF1 does not improve the predictive value of GH testing. As currently GH stimulation testing costs ~€1000, identification of other clinical or biochemical parameters are needed to reduce the necessity for repeat testing to diagnose IGHD.