Discrepancy between IGF-1 and GH suppression test in follow-up of the treated acromegaly patients

Introduction: Acromegaly, characterized by overproduction of growth hormone (GH) and insulin-like growth factor 1 (IGF1), increases the risk of mortality and morbidities. Monitoring is a crucial aspect of managing and treating of acromegaly patients. In various studies, patients with active acromegaly have shown discordance between GH and IGF-1 results after surgery. In this study, the discrepancy between these two tests in monitoring acromegaly patients was evaluated. Methods: The levels of IGF-1 and GH after OGTT in 49 acromegalic patients who underwent surgery at least 3 months earlier and had been referred to clinic for follow-up were analyzed. Clinical and metabolic parameters, GH nadir, and IGF-1 values were compared between groups. Results: Fifty-one percent of patients had normal IGF-1 based on their age and sex, and 57.1% of patients had GHn<1 µg/L. Based on IGF-1 and GHn results, 23 patients had discordant results. The most common pattern of discordance was high IGF-1 and normal GH nadir that was seen in 13 patients. A pattern of high GH and normal IGF-1 was seen in 10 patients. There was a significant difference between the corrected IGF-1 values of the high IGF-1 group and those of active disease group (P=0.001). There was no significant difference in GHn between high GHn group and active disease group (P=0.8). Conclusion: There is a significant inconsistency between the results of IGF-1 and GHn in monitoring of acromegaly patients. Also, when GH-0 is<1 µg/L the use of GHn does not help and there is a need for more frequent monitoring for early diagnosis of the disease recurrence.