From the Guidelines
Tyrosine in urine is primarily caused by disorders that affect tyrosine metabolism, with the most common causes including tyrosinemia type I, a genetic disorder resulting from fumarylacetoacetate hydrolase deficiency, as well as liver disease and Fanconi syndrome. The presence of tyrosine in urine, known as tyrosinuria, can be due to various factors that disrupt the normal metabolic pathway of tyrosine. According to the study by 1, tyrosinemia type I is a severe form of the disorder that leads to the accumulation of toxic metabolites, including succinylacetone, which can cause liver and kidney damage.
Causes of Tyrosinuria
- Tyrosinemia type I, resulting from fumarylacetoacetate hydrolase deficiency
- Liver disease, which can impair metabolic function and lead to tyrosinuria
- Fanconi syndrome, a kidney disorder that affects proximal tubule function and can lead to inappropriate excretion of tyrosine in urine
- Certain medications that affect liver function or compete with tyrosine for metabolism
- Transient tyrosinuria in newborns due to immature enzyme systems, especially in premature infants
- Dietary factors, such as high protein intake, which can temporarily increase tyrosine levels
Diagnosis and Treatment
Diagnosis of tyrosinuria typically involves urine amino acid analysis, and treatment depends on the underlying cause. As noted in the study by 1, treatment with NTBC (2-(2-nitro-4-fluoromethybenzoyl)21,3-cyclohexanedione) can result in rapid clinical and biochemical improvement in patients with hereditary tyrosinemia type 1. Dietary restrictions of tyrosine and phenylalanine, as well as medication adjustments or specific treatments for the primary disorder, may also be necessary. Regular surveillance with AFP and liver imaging is recommended to monitor for potential complications, such as hepatocellular cancer.
From the FDA Drug Label
The FDA drug label does not answer the question.
From the Research
Causes of Tyrosine in the Urine
- Tyrosine in the urine can be caused by genetic disorders such as Tyrosinemia, which is characterized by reduced activity of fumarylacetoacetate hydrolase (FAH), the final enzyme in the degradation of tyrosine 2.
- Tyrosinemia II is caused by a deficiency of hepatic tyrosine aminotransferase, leading to an increase in plasma tyrosine and tyrosine metabolites in the urine 3.
- Hereditary tyrosinemia type I (HTI) is an autosomal recessive disorder caused by deficiency of fumarylacetoacetase, which is the last enzyme in the tyrosine degradation pathway, resulting in accumulation of toxic metabolites in the liver and kidneys 4.
- Dietary factors, such as a high-tyrosine low-protein diet, can also contribute to the presence of tyrosine in the urine, as seen in a nutritional model of the disease in rats 3.
Underlying Mechanisms
- The enzyme block in Tyrosinemia causes accumulation of toxic metabolites in the liver and kidneys, leading to severe liver disease and potentially hepatocellular carcinoma 4.
- The deficiency of hepatic tyrosine aminotransferase in Tyrosinemia II leads to an increase in plasma tyrosine, causing tyrosine to crystallize in the cornea and producing corneal ulcerations and skin lesions 3.
- Treatment with NTBC in HT1 patients can lead to increased tyrosine concentrations, requiring strict dietary control to prevent neurocognitive problems 5.