Physiology Endocrinology and Reproduction 0b929645 Which vitamin acts as a hormone- A Niacin B Pyridoxin C Vitamin D D Riboflavin High-Yield Explanation Ans. is 'c' i.e., Vitamin D * Vitamin D and retinoic acid (Vitamin A) acts on endocrine intranuclear receptors and therefore are considered as hormonal Vitamin D.