Vitamin D Lecture Notes

Flashcards about Vitamin D

Vitamin D

Steroid hormone involved in immune response regulation, bone mineralization/metabolism, cell proliferation, and differentiation of various cell types.

Ergosterol

Vitamin D2 found in plants, not nutritionally important in the human diet.

7-Dehydrocholesterol

Provitamin D3 found in the skin that transforms into the active form via sunlight (UV rays).

1,25-dihydroxycholecalciferol (calcitriol)

The final active form of Vitamin D

Vitamin D3 (cholecalciferol)

Produced from 7-dehydrocholesterol (pro-vitamin D3) in the epidermis, a side-reaction product from the cholesterol-forming system.

Vitamin D2 (ergocalciferol)

Produced from ergosterol (pro-vitamin D2) upon exposure to ultraviolet B in plants.

25-hydroxylase

Enzyme in the liver that further activates vitamin D (D2 and D3).

1α-hydroxylase

Enzyme in the kidney that is responsible for the final activation of 25-hydroxy vitamin D to produce 1,25-dihydroxy vitamin D; stimulated by hypocalcemia and hypophosphatemia.

Vitamin D function: Calcium absorption

Increases the synthesis of calcium-binding protein in the intestinal mucosa to promote calcium absorption from the gut.

Vitamin D function: Growth of bones

Promotes bone growth by ensuring the deposition of calcium and phosphate.

Rickets

Condition of vitamin D deficiency in growing children, characterized by skeletal deformities and changes in bone and teeth.

Osteomalacia

Also known as adult rickets; bones are soft, fragile, and easily fractured.

Hypervitaminosis D

Rare condition from excessive vitamin D intake, leading to high calcium levels in the blood and affecting bones, tissues, and organs.