Endocrine Abstracts

Introduction: Paradoxical increase of growth hormone after glucose load (PR) and its clinical significance remain the focus of researchers. Different cut off points for diagnosis of PR are used in the literature.

Aim : Our aim was to investigate 3 different definitions of PR and their clinical implications.

Material and Methods: We analyzed 116 consecutive patients diagnosed with acromegaly in 2012-2022. We included 89 patients with available pituitary MRI, results of at least 3 GH values in the OGTT and hormonal evaluation before treatment. We used 3 definitions of PR. Definition 1(D1): increase of of GH at any time point of OGTT compared to baseline GH concentration. Definition 2 (D2): increase of at least 25%. Definition 3 (D3): increase of at least 50% occurring earlier than in 120’. For each definition, patients were divided into groups: with PR (PRpos), without PR (PRneg) and compared in terms of: GH concentrations during OGTT, IGF-1 and PRL and their upper limit of normal ratios, tumor volume, Signal Intensity Ratio (SIR) of the tumor and temporal grey matter. Response to SSA was assessed after 3-6 months of presurgical treatment in 69 patients, as the frequency of normalization of IGF1/ULN ratio and IGF1/ULN ratio decrease by ≥ 50%. This study was approved by the local Bioethics Committee (1072.6120.72.2020) and is part of statutory research of the Jagiellonian University Medical College (N41/DBS/000407).

Results: According to D1 60.7% of patients were PRpos, PRneg and PRpos differed in median nadir GH (15.05 uIU/ml IQR 23.6 vs. 26.4 I uIU/ml QR 49.2, P=0.012) and IGF1/ULN ratio (1.85 IQR 0,46 vs 2.44 IQR 1.05, P=0.002). Using D2, PRpos constituted 37.1% of patients. Median fasting GH concentration was higher in PRneg than in PRpos (10.23 ug/ml, IQR 14.19 vs 7.46 ug/ml, IQR 7.96, P=0.011). Using D3, 18% patients were PRpos, with no statistically significant differences between groups. The frequency of achieving normalization of IGF1 or decrease by at least 50% did not differ between PRpos and PRneg according to D1, D2, D3.

Conclusions: Even though we used 3 cut off points of PR, we observed no differences in responsiveness to presurgical treatment with SSA between PRpos and PRneg. However, further evaluation is required to understand the significance of PR and precise its exact definition.