“Hypotyrosinemia” in Phenylketonuria

Hanley, William; Lee, A.W.; Hanley, A.J.G.; Lehotay, Denis C.; Austin, Valerie; Schoonheyt, W. E.; Platt, B.A.; Clarke, Joe T.R.

doi:10.1006/mgme.2000.2985

Cited by 31 publications

(21 citation statements)

References 40 publications

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“…It should be noted that use of high concentrations of L-Tyr (1 mM) has only theoretical value, because the blood concentration of L-Tyr never exceeds 0.1 mM, either in healthy subjects or in patients with PKU. 26 Taken together these results suggest that L-Phe exerts its inhibitory action selectively on the NMDA subtype of ionotropic glutamate receptors.…”

Section: Specific Effect Of L-phe On I Nmdamentioning

confidence: 87%

Specific inhibition of N-methyl-D-aspartate receptor function in rat hippocampal neurons by L-phenylalanine at concentrations observed during phenylketonuria

et al. 2002

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Section: Specific Effect Of L-phe On I Nmdamentioning

confidence: 87%

Specific inhibition of N-methyl-D-aspartate receptor function in rat hippocampal neurons by L-phenylalanine at concentrations observed during phenylketonuria

et al. 2002

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“…Tyrosine as the product of the deficient enzyme phenylalanine hydroxylase becomes an essential amino acid in PKU [17]. For this reason, AAM are fortified with tyrosine.…”

Section: Discussionmentioning

confidence: 99%

Effects of Inadequate Amino Acid Mixture Intake on Nutrient Supply of Adult Patients with Phenylketonuria

Hochuli¹,

Bollhalder²,

Thierer³

et al. 2017

Ann Nutr Metab

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Background: Adult phenylketonuria (PKU) patients often reduce their intake of amino acid mixture (AAM) to less than the prescribed amounts. Effects of reduced AAM intake on nutrient supply were evaluated. Methods: Nutrient intake was calculated in 20 adult PKU patients based on a structured food record and complemented by laboratory assessment of nutritional status. Patients were classified into 2 groups, (A) regular AAM intake, or (B) AAM intake below calculated requirements. Results: Group B consumed a higher proportion of natural protein (60 ± 23 vs. 33 ± 12%, p = 0.002); however, the total protein intake was below the recommended amounts in 60% of patients in group B versus 7% in group A (p = 0.03). Fat intake was higher in group B (39 ± 9% of energy vs. 31 ± 6%, p = 0.03), mainly from saturated fats. Selenium, folate, and vitamin B12 intake was below the recommended intake in group B. However, serum concentrations of these analytes remained within the normal range in both groups, although vitamin B12 levels were lower in group B. Plasma tyrosine correlated with AAM intake, and hydroxyproline correlated with the amount of natural protein consumed. Conclusion: Relaxed AAM intake resulted in insufficient nutrient supply, despite a compensatory increase in consumption of natural protein. Care needs to be taken to ensure adequate nutrition in adults with PKU.

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“…Reduced or absent function of phenylalanine hydroxylase results in PKU and malfunction of the BH4 enzymes produces the biopterin deficiency variants. Tyrosine becomes an essential amino acid and because of the block in conversion of phenylalanine to tyrosine patients with PKU have low tyrosine levels (Hanley et al, 2000). Hence tyrosine supplementation to dietary therapy is often carried out.…”

Section: The Biochemistry Of Pkumentioning

confidence: 99%