The hypothalamus is part of the so-called 'gut-brain axis', where gastrointestinal hormones through interaction with the hypothalamus plays a significant role in the regulation of appetite and glucose metabolism. Incretins are the most prominent gastrointestinal hormones involved, with the incretin-effect referring to food-induced insulin secretion, which in healthy subjects is responsible for up to 70% of the insulin response after oral glucose intake. The investigators hypothesize that radiation conditional influence of the hypothalamus may compromise the gut-brain activity and thereby affect the incretin-effect and gastrointestinal-mediated glucose disposal (GIGD; i.e. sum of all gastrointestinal-derived factors that contribute to glucose metabolism) in patients with acromegaly. The aim of the study is to investigate the long term effect of surgery with or without additional fractionated radiation therapy on glucose metabolism as assessed by incretin-effect and GIGD in acromegaly, in order to identify possible associations with treatment modality.