Endocrine Abstracts

Recent Endocrine Society guidelines advocate IGF-1, random GH and nadir GH after oral glucose tolerance test (OGTT) for assessment in acromegaly. In our regional centre the 24 h GH profile has also been used partly because of changing IGF-1 assay methodology but also because of concerns that IGF-1 may not adequately reflect partial therapeutic success. We evaluated 58 GH profiles in 35 patients from April 2008 to November 2012 when both GH and IGF-1 assays remained unchanged. Samples were drawn every 2 h from 0800 to 0800 (13 time points) and matched with OGTT and IGF-1. In 20 patients paired profiles were available pre and 3 month postoperatively. Correlation between the mean 13 and five point (0800–1600) profile was strong (r=0.98, P<0.01). Correlations between the mean 13 point profile and nadir GH on OGTT and IGF-1 were also moderate-strong (r=0.96, P<0.01 and r=0.65, P<0.01 respectively). Preoperatively there was full concordance between 0800 GH and IgF-1 and GH profiles. Six patients had discordant results postoperatively (high 0800 GH ≥1 μg/l; normal IGF-1). Three of these had a 13 point mean of <1 μg/l. In the five patients with high 0800 GH (≥20 μg/l) preoperatively reductions in GH postoperatively were considerable (88–99%) and in one patient mean GH was <1 μg/l. In these five patients IGF-1 was not normalised being modestly reduced (34-64%) and in one patient, elevated by 33%.

Conclusions: GH profiling is not necessary in assessing the majority of patients with acromegaly if there is confidence in the local IGF-1 assay. When undertaken, a five point profile is adequate. In patients with high 0800 GH values profiling may more adequately reflect therapeutic effect than IGF-1. Further work is needed to explore the role of the GH profile in stratifying patients with discordant IGF-1 and GH results postoperatively.