The Association of Therapy Adherence and Thyroid Function in Adult Patients with Phenylketonuria

Abstract

Background: The standard, lifelong therapy of phenylketonuria (PKU) is a natural protein-restricted diet complemented with phenylalanine (Phe)-free L-amino acid mixtures that provide the daily necessary micronutrients. Objective: To assess thyroid function and structure and the iodine status of early-treated adult PKU (ETPKU) patients in Hungary. Methods: Sixty-nine PKU patients (aged 18–41 years) and 50 healthy controls were enrolled in the study. Thyroid hormones, serum thyroglobulin, thyroid antibodies, urinary iodine, and selenium concentrations were measured, and thyroid ultrasound was performed. Results: The incidence of thyroid dysfunction was infrequent (n = 2). Blood Phe was negatively correlated with thyroid-stimulating hormone (TSH), and PKU patients had higher free thyroxine and lower TSH levels than healthy controls. Although optimal iodine status was found in the entire PKU population, by dividing the patients according to their therapy compliance, we observed that lower therapy adherence was associated with mild iodine deficiency and lower urinary selenium levels. Conclusions: The results of this study suggest that iodine status is strongly influenced by the adherence to therapy in ETPKU patients. No or not enough medical food consumption combined with a low-Phe diet can lead to subclinical iodine deficiency.

Biomarkers of Micronutrients in Regular Follow-Up for Tyrosinemia Type 1 and Phenylketonuria Patients

“…With tyrosine being the precursor of thyroxin, it can be hypothesized that altered tyrosine concentrations, as observed in PKU and TT1, may have an influence on thyroxin availability which can be assessed by measuring TSH levels. Our results did not show clear aberrations in TSH levels, which is in contrast with Sumanszki et al who did observe lower TSH levels in adult PKU patients compared to controls [25]. Therefore, the possible effect of tyrosine (and phenylalanine) concentrations on thyroid function should be investigated in more detail.…”

Cord blood metabolomics reveals gestational metabolic disorder associated with anti-thyroid peroxidase antibodies positivity

“…Supplementation with L-Tyrosine is commonly used to support thyroid function, leading to a reduction in TSH [ 45 , 46 ]. A low phenylalanine diet was report to contribute to subclinical iodine deficiency [ 47 ]. The fluctuations of all the ten metabolites induced by anti-TPO antibodies positivity in the present study were in accordance to their previously reported status in hypothyroidism, indicating that anti-TPO antibodies positivity contributes to a metabolic disorder prone to hypothyroidism.…”

The Impact of the Quality of Nutrition and Lifestyle in the Reproductive Years of Women with PKU on the Long-Term Health of Their Children

“…Vitamin B12 [ 41 , 45 ], zinc [ 21 , 46 ], and selenium [ 21 , 41 , 47 ] inadequacies are also reported in adult patients. Lower dietary adherence is associated with mild iodine deficiency and lower urinary selenium levels [ 48 ]. Pregnancy also increases the requirements for several macro- and micro-nutrients, compounding the risk of nutritional imbalance in women.…”

“…A meta-analysis by Levie et al showed that a lower urinary iodine-to-creatine ratio during pregnancy was associated with a lower verbal IQ [ 75 ]. In women with PKU, iodine status is strongly influenced by a dietary adherence to protein substitutes supplemented with micronutrients, the main dietary source of iodine [ 21 , 22 , 48 , 74 , 76 ].…”