Failure of alpha-methyltyrosine to inhibit peripheral triiodothyronine formation.
To determine if the adrenergic nervous system, and specifically tyrosine hydroxylase, plays a role in the extrathyroidal conversion of T4 to T3, normal male volunteers were treated with T4 and subsequently with T4 and alpha-methyl-p-tyrosine (alpha-MPT), an inhibitor of tyrosine hydroxylase, for 2 weeks. The mean serum T4 and T3 concentrations increased during T4 administration and remained at the same levels during combined T4 and alpha-MPT administration. Urinary vanillylmandelic acid excretion declined significantly during alpha-MPT administration. These results do not support the hypothesis that tyrosine hydroxylase is involved in extrathyroidal T3 production.
D000328:Adult; D006801:Humans; D007700:Kinetics; D008297:Male; D008781:Methyltyrosines; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000096:biosynthesis* / Q000097:blood; D014446:Tyrosine 3-Monooxygenase / Q000037:antagonists & inhibitors*; D019805:alpha-Methyltyrosine
D008781:Methyltyrosines; D014284:Triiodothyronine; D019805:alpha-Methyltyrosine; D014446:Tyrosine 3-Monooxygenase; D013974:Thyroxine