Abstract Background Recent evidence correlates Alzheimer‘s disease (AD) and diabetes mellitus (DM), through the involvement of reduced insulin–like growth factor (IGF–1). In acute myocardial infarction (AMI), low IGF–1 levels are correlated with a high risk of mortality and re–infarction. However, the DM–amyloid 1–40 (Aβ1–40) association in patients with coronary artery disease (CAD) remains unexplored. Aim and Methods To study Aβ1–40 concentrations based on glycaemic status, identify predictors of its levels, and assess the relationship between this peptide and IGF–1, we collected blood samples from 630 AMI patients on admission. Patients were classified into three groups based on haemoglobin A1c (HbA1c) levels: group 1 (189 patients without DM, HbA1c<39 mmol/mol), group 2 (270 patients with pre–DM, HbA1c 39–48 mmol/mol), and group 3 (171 patients with DM, HbA1c>48 mmol/mol). Results The cohort, mostly male (73.5%), had a mean age of 66.33 (11.28) years. Among them, 74.85% presented with ST–elevation myocardial infarction (STEMI), and 25.2% had a history of previous ischemic events. Median Aβ1–40 levels were 85.75 [53.85–128.67] pg/ml. Aβ1–40 positively correlated with age, tumor necrosis factor–alpha, HbA1c, HOMA–IR index, and TyG index. No significant correlation was observed between Aβ1–40 and IGF–1. Aβ1–40 levels increased from group 1 to group 3 (72.42 [48.79–109.26] pg/ml vs. 86.25 [53.4–125.54] pg/ml vs. 103.56 [61.78–46.31] pg/ml, respectively, p<0.001). Although not statistically significant, DM patients tended to have lower IGF–1 values compared to those without DM, while pre–DM patients had the lowest values, suggesting poorer glycaemic control (groups 1, 2, and 3: 575.3 [326.75–864.75] pg/ml vs. 519.25 [294.08–800.48] pg/ml vs. 528.3 [216.2–836.6] pg/ml). At logistic regression analysis, high levels of Aβ1–40 were predicted by older age, worse left ventricular systolic function, higher HOMA–IR index, higher levels of HbA1c, and poorer glomerular filtration rate (GFR), corrected by vitamin D. Conversely, lower levels of IGF–1 were predicted by older age, higher TyG index, higher HbA1c, low vitamin D levels, and compromised GFR. Conclusions Given the established link between Aβ1–40 and mortality in AMI patients, improved glycaemic control could reduce the levels of this peptide, counteract its pro–inflammatory properties and improve prognosis. Further investigations are needed to clarify the complex relationship between Aβ1–40 and IGF–1.