Reductions in tyrosine levels are associated with thyroid hormone and catecholamine disturbances in sepsis

Introduction The magnitude of fall in thyroid hormone and rise in catecholamine levels are prognostic in critical illness (1, 2). These may be linked, as the amino acid tyrosine is converted by tyrosine hydroxylase to L-DOPA, and thence to dopamine, norepinephrine and epinephrine, whereas thyroxine (T4) and tri-iodothyronine (T3) are formed by the iodination of tyrosine residues in thyroglobulin. We used our well-characterized 72 h fluid-resuscitated rat model of faecal peritonitis, where accurate prognostication can be made as early as 6 h (3), to explore any relationship.