Objective The aim of this study was to describe endocrinological outcome in patients operated on for acromegaly. Methods A retrospective study included 167 patients. Patients were assessed in the early postoperative period (EPP), at 3 months (M3), at 1 year (Y1), and then annually. They were classified as grade I (IGF-1 level normal-for-age and positive GH response on oral glucose tolerance test [nadir <0.4 ng/L]); grade II (discordant); or grade III or IV (acromegaly, controlled or uncontrolled under medical therapy, respectively). Results Taking all patients with all grades, 35% changed grades between EPP and M3, 26% between M3 and Y1 and 9% after Y1. In grade I, respectively 22%, 15% and 2% of patients changed grades between EPP and M3, between M3 and Y1, and after Y1, compared to 31%, 6% and 6% in grade IV. Respectively 57%, 67%, and 47% of grade II patients changed grades between EPP and M3, between M3 and Y1, and after Y1; between EPP or M3 and last follow-up (>1 year), respectively 74% and 75% of grade II patients changed grades. Knosp category, resection quality and abnormal GH response (vs. abnormal IGF-1) significantly impacted grade II patients’ outcome. Conclusions Whereas outcome in grades I and III–IV seems to be determined by 1 year, grade II discordant patients’ outcome remains uncertain even after 1 year.