Remission of
acromegaly is defined as a nadir in GH <1.0 ng/mL during a 75-g oral
glucose tolerance test (75gOGTT) and
insulin-like growth factor-1 (IGF-1) normalization. Recently, a lower cut-off value for GH nadir (<0.4 ng/mL) has been proposed. We retrospectively evaluated the prevalence and clinical characteristics of postoperative cases with normalized
IGF-1 levels and a GH nadir of 0.4-1.0 ng/mL one year after complete resection of
GH-secreting pituitary adenoma (GHoma). We included 110 cases of
acromegaly with complete
adenoma resection, no preoperative treatment, preoperative
glycosylated hemoglobin <6.5%, preoperative basal plasma
glucose <126 mg/dL, GH nadir <1.0 ng/mL during a 75gOGTT, and normalized
IGF-1 at the first postoperative year evaluation, whereupon patients were divided into two groups: control (GH nadir <0.4 ng/mL) and high GH (GH nadir >0.4 ng/mL). Clinical parameters, including measures of insulin secretion and resistance, were compared between groups. The high GH group included 10 patients (9.1%) and had a lesser level of
insulin resistance immediately following surgery and at the first postoperative year evaluation. On single regression analysis,
insulin resistance immediately following surgery was predictive of and correlated with the GH nadir at the first postoperative year evaluation. The GH nadir at the first postoperative year evaluation may be insufficient in patients with normalized
IGF-1 with low
insulin resistance immediately following complete resection of GHoma. Careful evaluation is needed to assess remission in such patients.