Vitamin D aids in the absorption of calcium and has central roles in bone formation and maintenance, hypertension, cancer, and immunity. Vitamin D2 is produced in fungi, including yeast, from ergosterol in response to ultraviolet radiation. 25-hydroxy Vitamin D2 is an intermediate produced from vitamin D2 by cytochrome P450 isoforms in vertebrates. It is subsequently metabolized to 1,25-dihydroxy vitamin D2, which is an agonist for the vitamin D receptor.
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