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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
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Vitamin also acting as hormone
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The correct answer is  Vitamin D is not strictly a vitamin since it can be synthesized in the skin the dietary source is required only when sunlight exposure is inadequate Its main function is in the regulation of calcium absorption and homeostasis most of the actions of vitD mediated by nuclear receptors. ref harpers biochemistry 30th ed page 551