title: Extremely elevated international normalized ratio of warfarin in a patient with CYP2C9*1/*3 and thyrotoxicosis.
abstract: A 73-yr-old Korean man with permanent atrial fibrillation visited outpatient clinic with severely increased International Normalized Ratio (INR) values after taking a usual starting dosage of warfarin to prevent thromboembolism. We found out later from his blood tests that he had hyperthyroidism at the time of treatment initiation. His genetic analysis showed CYP2C9*1/*3 and VKORC1+1173TT genotypes. We suspect that both hyperthyroidism and genetic variant would have contributed to his extremely increased INR at the beginning of warfarin therapy. From this case, we learned that pharmacogenetic and thyroid function test might be useful when deciding the starting dosage of warfarin in patients with atrial fibrillation.
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Ji Eun
authors.identifier: 0000-0002-8660-0861
authors.initials: JE
authors.lastname: Lee
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Duck Hyun
authors.identifier: 0000-0003-1426-8318
authors.initials: DH
authors.lastname: Ryu
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Ho Jung
authors.identifier: 0000-0003-2944-2294
authors.initials: HJ
authors.lastname: Jeong
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Jung Hoon
authors.identifier: 0000-0003-3140-1328
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Ji Eun
authors.identifier: 0000-0002-7204-4913
authors.initials: JE
authors.lastname: Jun
authors.affiliation: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: June Soo
authors.identifier: 0000-0001-7569-6450
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Soo Youn
authors.identifier: 0000-0002-0662-7408
authors.initials: SY
authors.lastname: Lee
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000097:blood / Q000378:metabolism / Q000627:therapeutic use; D001241:Aspirin / Q000627:therapeutic use; D001281:Atrial Fibrillation / Q000175:diagnosis*; D002851:Chromatography, High Pressure Liquid; D065729:Cytochrome P-450 CYP2C9 / Q000235:genetics*; D005838:Genotype; D006801:Humans; D008297:Male; D020641:Polymorphism, Single Nucleotide; D053719:Tandem Mass Spectrometry; D013923:Thromboembolism / Q000517:prevention & control; D013971:Thyrotoxicosis / Q000175:diagnosis*; D064417:Vitamin K Epoxide Reductases / Q000235:genetics; D014859:Warfarin / Q000097:blood* / Q000378:metabolism / Q000627:therapeutic use
chemical_list: D000925:Anticoagulants; D014859:Warfarin; D065729:Cytochrome P-450 CYP2C9; C578523:VKORC1 protein, human; D064417:Vitamin K Epoxide Reductases; D001241:Aspirin
keywords: Genotype; International Normalized Ratio; Thyrotoxicosis; Warfarin