Endocrine Abstracts

NICE guidelines (2010) recommend two different GH provocation tests demonstrating subnormal peak GH levels to diagnose isolated GH deficiency (GHD). Choice of stimulation test varies in different units. In our centre, glucagon (GST) and clonidine (CST) stimulation tests are used to make a diagnosis of IGHD. IGF1 is done as part of the initial screening tests.

Purpose of this study was to compare the GST vs CST and to establish if IGF1 level provided any extra information. GH assay at our centre sets a peak GH level of >7 μg/l as normal.

44 children who underwent two GH stimulation tests were included. IGF1 levels measured in 42 children prior to GH tests. Whilst 33/44 (75%) had GST as first test, 11/44 CST as first test. Of the 33 children with subnormal GST (peak <7 μg/l), 21 (64%) had normal response to CST. Of the 11 children with subnormal CST, 1 (9%) subsequently had normal response to GST but 91% diagnosed to have GHD after GST. No difference in age group of the children in both groups (median age 8.3 years CST first test vs 10.7 years GST first test) was identified. Results of IGF1 did not provide any additional information. 74% (17/23) of those diagnosed GHD had low IGF1 levels (8/10 with GHD in CST group vs 9/13 in GST group).

Significant proportion who failed GST (first test) showed normal response in subsequent CST compared to those who had CST as first test. There were no predictors to choose either test as a first choice and hence avoid a second test if possible. Until a ‘gold standard biomarker’ of GHD becomes available, current NICE guideline recommendation of two GH tests to diagnose IGHD stands with no evidence of choice of GST or CST as first test.