Vitamin D Biochemistry
View this Vitamin D Biochemistry mnemonic and other USMLE mnemonics in the Vitamins playlist.

Vitamin D Biochemistry

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Vitamin D is a fat-soluble vitamin that exists in a number of different forms. Ergocalciferol (D2) is a less potent form of vitamin D found in plants, whereas cholecalciferol (D3) is a more potent form synthesized in the skin after exposure to sunlight. In addition, dairy products may be fortified with vitamin D3.

After ingestion or synthesis, vitamin D (calciferol) undergoes hydroxylation in the liver to form 25-hydroxy Vitamin D (calcidiol), the inactive storage form of vitamin D. Later, calcidiol undergoes further hydroxylation in the kidney, forming the active form: 1,25-dihydroxy vitamin D (calcitriol).

Active vitamin D operates at the kidneys, GI tract, and bone to control calcium and phosphate levels. At low levels, it leads to increased bone mineralization. At high levels, it leads to increased bone resorption, thereby increasing calcium and phosphate levels.

Find Vitamin D Biochemistry and other Vitamins among Pixorize's visual mnemonics for the USMLE Step 1 and NBME shelf exams.