<unk>  is a form of Vitamin D, also called vitamin<unk> . 
It is structurally similar to steroids such as testosterone, cholesterol, and cortisol (though vitamin<unk>  itself is a secosteroid).
1g of pure vitamin<unk>  is 40 000 000 (40x106) IU, or in other words, one IU is 0.025 μg.
Cholecalciferol
Ergocalciferol
Doxercalciferol 
Vitamin D
Calcitriol 
Folic acid 
Tocopherol
Menadione