Effect of large neutral amino acids treatment on blood phenylalanine, tyrosine, and tryptophan levels in adolescent and young adult PKU patients

Objective: We aimed to evaluate the change in phenylalanine (Phe), Tyrosine (Tyr), and Tryptophan (Trp) blood levels in classical PKU patients treated with large neutral amino acids (LNAA) supplementation. Methods: Twenty-nine PKU patients treated with LNAA between 2013-2022 were enrolled in the retrospective observational study. Four cases were excluded from the statistical analysis due to missing data. Results: The median age (min-max) onset of LNAA was 11.6 (8-38.1) years, and the median duration (min-max) of LNAA use was a median of 42.7 (5-105) months. The mean current age of the patients was 19.70±9.96 years. The final blood levels of Phe, Tyr, and Trp did not change significantly (p>0.05) from the baseline. At the last measurement, the Hb value increased significantly (p0.05). It was seen that there was an increase in the employees’ productivity at work, the success of the students in the course, and the focus on maintaining attention. Conclusions: We want to highlight that LNAA could be a treatment option for adolescents or adults who are not adhering to a Phe-restricted diet.