Effects of transsphenoidal adenomectomy on glucose metabolism and free fatty acid induced insulin resistance in acromegaly

Abstract

Background: Acromegaly is frequently accompanied with abnormal glucose metabolism. Underlying mechanisms are unclear as are the factors that influence abnormal glucose tolerance. In addition, the effects of the transsphenoidal adenomectomy (TSA) on glucose metabolism and free fatty acid (FFA) have not been well studied. The aim of this study was to investigate the factors associated with abnormal glucose tolerance and the effects of TSA on glucose metabolism and FFA induced insulin resistance in acromegaly. Methods; A total of 228 Patients with GH secreting pituitary adenoma were enrolled. All of them were treated with TSA, and were evaluated with 75 g oral glucose tolerance tests (75 g OGTT) at 6 month intervals for at least 1 year after TSA. Growth hormone (GH), insulin-like growth factor 1 (IGF-1), glucose and FFA were measured before and after surgery. The remission of acromegaly was considered as GH nadir < 1ng/mL by 75g OGTT. After TSA, magnetic resonance image was taken for determine the extent of tumor resection. Data, collected up to one year after surgery, were used to compare with baseline findings.Result: The mean age at the time of surgery was 43.3 ± 0.5 years, and the male/female ratio was 0.76 (99/129). Initial GH and IGF-1 were 23.6 ± 21.8 and 702.0 ± 277.8, respectively. Remission with total resection (RT), non-remission with total resection (NRT), and non-remission with subtotal resection (NRS) were 83.7%, 7%, and 8.4% of total patients, respectively. After TSA, glucose, FFA and hemoglobin A1c (HA1c) were significantly decreased in RT (p=0.001), homeostasis model assessment of insulin resistance was significantly improved in RT and NRT groups (p=0.001), accompanied with reduction of GH. Incidence of diabetes mellitus (DM) was reduced (42.5% to 23.7%), and while normal glucose tolerance (NGT) was increased (34.4% to 64.0%), significantly in RT and NRT than NRS (p=0.001). Conclusion: Glucose and FFA were significantly reduced, and HOMA-IR was normalized after TSA with total resection. The improvement in insulin resistance appeared to result from the reduction of GH, as measured by HOMA-IR and FFA.