维生素D在维持钙的体内平衡方面起着重要的作用。在小肠、皮肤、骨和肾脏都有丰富的维生素D受体,起着调节血清钙水平的作用。有意义的是,维生素D受体也存在于其它几个与钙的代谢无关的器官,例如视网膜、胰腺、脑下垂体、肌肉、女性生殖器官、脑、骨髓以及胸腺。这些与钙代谢无关的正常组织内的维生素D受体的作用还不清楚。研究者们推测维生素D可能起着一种广泛地催化细胞成熟的作用。人类的几种恶性肿瘤,如乳腺癌、结肠 Vitamin D plays an important role in maintaining calcium homeostasis. Rich in vitamin D receptors in the small intestine, skin, bones, and kidneys, plays a role in regulating serum calcium levels. Significantly, vitamin D receptors are also found in several other organs that are not involved in the metabolism of calcium, such as the retina, pancreas, pituitary gland, muscle, female reproductive organs, brain, bone marrow, and thymus. The role of these vitamin D receptors in normal tissues unrelated to calcium metabolism is unclear. Researchers speculate that vitamin D may play a role in a broad spectrum of cell maturation. Several human malignant tumors, such as breast cancer, colon