This experimentally induced hyperthyroidism rapidly induced cardiomyopathy as evidenced by marked increases in HR, SBP, and LVESP, and further examination revealed multiple signs indicative of myocardial hypertrophy, including greater dry heart/body weight ratio16, elevated serum concentrations of NT-proBNP and FGF-23, myocardial upregulation of the remodeling marker MMP-9, collagen fiber accumulation17, and upregulation of various fibrotic marker genes and the regulatory miRNA let-7b18. Here, MMP9 is linked to hyperthyroidism.