After treatment with AMR and its fractions, the high expression of Hadha, Haao, Cyp1a2, the high level of 3-indoleacetic acid and isoquinoline, the low expression of cat, aldh2, Ehhadh, and xanthurenic acid were significantly reversed in hypothyroidism rats, indicating that AMR and its splitted fractions could ameliorate abnormal tryptophan metabolism. Here, CAT is linked to hypothyroidism.