Sumanszki C, et al. - Researchers analyzed a sample of 69 phenylketonuria (PKU) patients (aged 18–41 years) and 50 healthy controls to evaluate thyroid function and structure and the iodine status of early-treated adult PKU (ETPKU) patients in Hungary. They measured thyroid hormones, serum thyroglobulin, thyroid antibodies, urinary iodine, and selenium levels, and performed thyroid ultrasound. They reported infrequent (n=2) incidence of thyroid dysfunction. Higher free thyroxine and lower thyroid-stimulating hormone levels were detected among PKU patients vs healthy controls. Findings revealed a strong impact of adherence to therapy on iodine status in ETPKU patients; mild iodine deficiency and lower urinary selenium levels were observed in relation to lower therapy adherence. Subclinical iodine deficiency may occur due to no or not enough medical food intake combined with a low-Phe diet.