Prevalence and risk factors of impaired glucose tolerance and diabetes mellitus at diagnosis of acromegaly: a study in 148 patients

Acromegaly is frequently associated with alterations of glucose metabolism but factors predisposing these patients to exhibit impaired glucose tolerance or overt diabetes at diagnosis are poorly understood. This study included 148 patients with newly diagnosed acromegaly (80 men; mean age: 45 ± 20 year). All patients underwent an oral glucose tolerance test (OGTT), unless already treated for diabetes. Insulin sensitivity (S) and β-cell function (B) were also evaluated by homeostasis model assessment (HOMA). Normal glucose tolerance (NGT) was observed in 67 patients (46 %), impaired fasting glycaemia (IFG) or glucose tolerance (IGT) were found in 39 (26 %), and diabetes mellitus (DM) in 42 (28 %). NGT patients were 10 years younger than patients with abnormal glucose metabolism (p < 0.001) and diabetic patients had a higher BMI (p < 0.05). While HOMA-S was similar, HOMA-B was reduced in the IFG/IGT group (p < 0.05) and further in the DM group (p < 0.001). IGF-I z-score was higher in IFG/IGT (5.2 ± 1.4) and DM patients (5.4 ± 1.3) than in NGT patients (4.4 ± 1.3; p < 0.05), but fasting and post-OGTT GH levels were not different between groups. In multivariate analyses, family history of diabetes and IGF-I were associated with hyperglycaemia, BMI and IGF-I predicted insulin resistance, and age was inversely correlated with β-cell function. Impaired glucose metabolism is present in more than 50 % of patients at diagnosis of acromegaly, and is associated with an older age, a higher BMI, a family history of diabetes and a higher IGF-I z-score, but not with fasting or post-OGTT GH levels.