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How do the skin, liver, and kidneys work together to make vitamin D active?
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human endocrine system
The principal glands of the female and male human endocrine systems.
The process of activating vitamin D involves a coordinated sequence of chemical transformations across the skin, liver, and kidneys.
- Skin: Vitamin D production begins in the skin, where ultraviolet radiation from sunlight converts 7-dehydrocholesterol into cholecalciferol (vitamin D).1
- Liver: Once formed in the skin or obtained through the diet, these inactive precursors are transported to the liver. There, they are converted into calcidiol (25-hydroxyvitamin D).1
- Kidneys: Calcidiol is then transported to the kidney tubules. Under the stimulation of parathyroid hormone, the kidneys convert calcidiol into calcitriol (1,25-dihydroxyvitamin D), which is the most potent, biologically active form of the vitamin.12
Once activated, calcitriol enters the circulation and travels to the small intestine, where it plays a critical role in increasing the efficiency of dietary calcium and phosphorus absorption.12