This study investigates the metabolic effects of hypertrophic cardiomyopathy (HCM) in cats (n = 27; 13 cats in categories B1 + B2 and 14 cats in categories C + D) by analyzing serum concentrations of insulin-like growth factor-1 (IGF-1), 26S proteasome (26S PSM), and 3-methylhistidine (3-MH). This evidence concerns the gene IGF1 and hypertrophic cardiomyopathy.