Objectives: We aimed to investigate the clinical, biochemical, histological and radiological characteristics as well as the response to somatostatin analogs (SSA) in a large cohort of acromegaly patients with a paradoxical GH response (PR) to oral glucose tolerance test (OGTT).
Design: retrospective study.
Methods: Of 110 patients with acromegaly included in our study, 30 (PR+; 27%) had a paradoxical GH increase of more than 25% relative to basal GH levels during OGTT.
Results : At diagnosis, PR+ patients were older than PR- patients (52 ± 16 vs 44 ± 14 years, p<0.05) and had smaller pituitary tumours (40% microadenomas vs 19%, p<0.05), which were less often invasive (17 vs 35%, p<0.05), overall more secreting (IGF-1/tumoural surface: 2.35 ULN/cm² [0.28-9.06] vs 1.08 [0.17- 7.87], p=0.011), and more often hypointense on T2-weighted MRI (92 vs 48%, p=0.001). While the rate of remission after surgery was similar in the two groups (69%), a better response to SSA treatment was observed in PR+ patients, either before (IGF-1 reduction of > 50% after 3-6 months in 77 vs 49%, p=0.023) or after surgery (normalization of IGF-1 in 100 vs 44%, p=0.011).
Conclusions: Our study demonstrates that in acromegaly, a paradoxical GH increase during OGTT is associated with particular features of somatotroph adenomas and with a better prognosis in terms of response to somatostatin analogs.