Endocrine Abstracts (2011) 26 P230

Comparison of GH suppression response after oral and intravenous glucose tolerance tests in healthy subjects

Cevdet Aydin, Reyhan Ersoy, Didem Ozdemir, Neslihan Cuhaci, Dilek Arpaci, Alper Usluogullar, Yusuf Ustu, Husniye Baser, Ahmet Dirikoc & Bekir Cakir

Department of Endocrinology and Metabolism, Ataturk Education and Research Hospital, Ankara, Turkey.

Introduction: In this study, we aimed to compare GH values obtained in oral glucose tolerance test (OGTT) and intravenous glucose tolerance test (IVGTT) in healthy individuals.

Material and methods: Data of 18 healthy volunteers were analysed (10 male and 8 female). Firstly all subjects were evaluated with 75 g oral glucose tolerance test. In another day, intravenous glucose tolerance test was performed. Serum glucose, insulin and GH levels obtained during two tests were measured.

Results: Basal GH levels had a wide distribution ranging from 0.00005 μg/l (0.05 pg/ml) to 0.768 μg/l (768.92 pg/ml) (median 0.0145 μg/l). Mean nadir GH level during OGTT was 0.0376 μg/l (between 0.00011 and 0.387, median 0.0016, S.D.: 0.095, S.E.M.: 0.038) and it was obtained at 60th minute. Nadir GH level during IVGTT was observed at 10th minute and it was 0.112 μg/l (between 0.0005 and 0.770, median 0.0053, S.D.: 0.242, S.E.M.: 0.057). There was statistically significant difference between GH levels at 10th minute in IVGTT and at 60th minute in OGTT (Z=2.201, P=0.028). GH level at 10th minute in IVGTT was higher than GH level at 60th minute in OGTT.

Conclusions: Effect of gastroenteropancreatic pathway which may show individual differences can be eliminated by IVGTT. GH suppression by IVGTT may be used in the diagnosis and follow-up of patients with acromegaly. Higher nadir GH levels in IVGTT indicates that nadir GH levels suggested for remission in acromegalic patients are relatively low. Our results show that there may be need to revise the remission criteria for acromegaly.

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