Prevalence and patterns of biochemical discordance in patients with surgically treated acromegaly

OBJECTIVE: Discordance between growth hormone (GH) and insulin-like growth factor-1 (IGF-1), where one hormone is within the age- and sex-adjusted reference and the other is not, can be observed in patients with acromegaly. The discrepancy complicates the interpretation of disease activity, thereby presenting a significant challenge in the clinical management of acromegaly. This study aimed to assess postoperative discordance prevalence and clinical correlates to clarify the implication of discordance. METHODS: This retrospective study describes a cohort of patients that has undergone pituitary surgery at Sahlgrenska University Hospital between 1994 and 2019 due to acromegaly. Medical records were reviewed and the group with postoperative discordant hormones was compared with the group with concordant hormones. RESULTS: In a cohort of 82 patients surgically treated for acromegaly and thereafter examined with an oral glucose tolerance test (OGTT), 16 (19.5%) exhibited biochemical discordance. Fourteen of 16 patients showed elevated IGF-1 but normal GH. The IGF-1 levels at diagnosis were significantly higher in patients with discordance compared with the controlled concordant group. However, no differences were observed between the discordant and the concordant group regarding the baseline variables at diagnosis: age, gender, invasive tumour, micro/macro-adenoma or BMI, nor hypertensive treatment at time of surgery and postoperative radiotherapy or reoperation. CONCLUSION: The prevalence of biochemical discordance in our cohort was 19.5%. The predominant pattern was elevated IGF-1 levels with a normal nadir GH. The discordant group had higher IGF-1 at diagnosis, suggesting that greater preoperative disease activity may predispose to postoperative biochemical discordance.