Between 1 and 3 months after surgery 356 ml blood will be drawn. The patient will again be examined 12 months after surgery and 383 ml blood is drawn including blood samples for the endocrinology follow up-visit. All patients are substituted with iron and B12 vitamin from inclusion in the study and will prior to studies be examined with a spot hemoglobin (HB). Should the HB < 6,5 mmol/ l the study will be postponed for 3-5 weeks.