The byproducts of tyrosine catabolism serve as intermediates in the TCA cycle, and dysregulation of this process contributes to the progression of hepatocellular carcinoma.456 Deficiencies in the tyrosine metabolic enzyme 4-hydroxyphenylpyruvate dioxygenase (HPD) lead to mTOR activation, promoting the accumulation of TCA cycle intermediates, such as citrate, α-KG, succinate, fumarate, and malate. This evidence concerns the gene HPD and hepatocellular carcinoma.