This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Thyroxine is synthesized from: \nSelect and explain. \nA. Phenylalanine, B. Tryptophan, C. Tyrosine, D. None of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: In dopaminergic cells in the brain, tyrosine is conveed to levodopa by the enzyme tyrosine hydroxylase (TH).TH is the rate-limiting enzyme involved in the synthesis of the neurotransmitter dopamine.In the adrenal medulla, tyrosine is conveed into the catecholamine hormones norepinephrine (noradrenaline), and epinephrine.The thyroid hormones triiodothyronine (T3) and thyroxine (T4) in the colloid of the thyroid also are derived from tyrosine.', 'role': 'assistant'}]