Vitamin K is a family of fat-soluble vitamins essential for normal blood-clotting function and comprises two vitamers that are found naturally: phytomenadione (also known as phylloquinone or K1) and menaquinone (or K2).
Menadione is a synthetic molecule which is occasionally called vitamin K3 however this is a misnomer as it is not found in nature. It used to be used to treat hypovitaminosis K in neonates but is now banned due to toxicity at higher doses. which is not seen with the naturally-occurring vitamins K1 and K2.
Menaquinone is synthesised by normal flora in the intestine although the amount produced in vivo in the human gut is likely negligible. Vitamin K serves as a coenzyme for the clotting factors II, VII, IX and X. Warfarin inhibits vitamin K by preventing its enzymatic reactivation.
Pathological manifestations are rare.
Hypovitaminosis K can lead to jaundice and anemia in the neonate.
Hypervitaminosis K is extremely rare but when present may cause thrombophilia or hemolysis 3.
- 1. Pamela C. Champe, Richard A. Harvey (Ph. D.), Denise R. Ferrier. Biochemistry. ISBN: 0781769604
- 2. DiNicolantonio, J., Bhutani, J. and O'Keefe, J. (2015). The health benefits of vitamin K. Open Heart, 2(1), p.e000300. doi: 10.1136/openhrt-2015-000300
- 3. Florian Lang. Encyclopedia of Molecular Mechanisms of Disease. (2009) ISBN: 9783540671367
Related Radiopaedia articles
- tumor markers
- chemical elements
- fat-soluble vitamins
- vitamin B1 (thiamine)
- vitamin B2 (riboflavin)
- vitamin B3 (niacin)
- vitamin B5
- vitamin B6
- vitamin B7 (biotin)
- vitamin B9 (folate/folic acid)
- vitamin B12
- vitamin C
- B vitamins