Insulin-like growth factor-1 (IGF-1) is important in the hypertrophic response of the myocardium, so the present study was designed to elucidate whether the circulating levels of IGF-1 and its binding proteins (IGFBPs) are related to the disease condition of patients with hypertrophic cardiomyopathy (HCM), in particular the occurrence of congestive heart failure (CHF). The study group comprised 124 patients with HCM and 15 healthy control subjects. The HCM patients were subdivided into 3 groups: 39 with hypertrophic obstructive cardiomyopathy (HOCM), 67 with hypertrophic non-obstructive cardiomyopathy (HNCM), and 18 with HCM and a history of CHF (HF-HCM, n=18). Serum levels of IGF-1 and IGFBPs (IGFBP-1 and -3) were compared between groups. IGF-1 levels were significantly higher in patients with HOCM and HNCM, and lower in patients with HF-HCM than in control subjects (p<0.0001, p<0.005, and p<0.05, respectively). IGFBP-1 levels were significantly higher in patients with HF-HCM than in the other 3 groups (p<0.0001 for all). The findings suggest that circulating levels of IGF-1 and IGFBP-1 are related to the extent of myocardial injury in patients with HCM.