Identification and determination of the urinary metabolite of iodotyrosine invivo.

Background: Congenital hypothyroidism screening traditionally relies on detecting elevated thyroid-stimulating hormone levels, yet this approach may not detect a specific type of congenital hypothyroidism caused by iodotyrosine dehalogenase-1 (Dehal1) deficiency. The deficiency of this enzyme prevents the deiodination of mono-iodotyrosine (MIT) and di-iodotyrosine (DIT) in the process of iodine recycling. This underscores the potential use of iodotyrosine or its metabolites as non-invasive urinary biomarkers for early diagnosis of congenital hypothyroidism.