7dehydrokolesterolin

7dehydrocholesterol is a sterol that is the immediate precursor to vitamin D3 in the skin of humans and other animals. It is a cholesterol derivative found in the skin and is essential for the synthesis of vitamin D. When skin is exposed to ultraviolet B (UVB) radiation from sunlight, 7dehydrocholesterol undergoes a photochemical reaction. This reaction opens one of the rings in its structure, forming pre-vitamin D3. Pre-vitamin D3 is then isomerized into vitamin D3 (cholecalciferol) through a heat-dependent process. This process is a crucial step in how the human body obtains vitamin D, which is vital for calcium absorption and bone health. A deficiency in 7dehydrocholesterol can impair vitamin D production. Conversely, adequate levels are maintained through normal cholesterol metabolism. It is found in the stratum basale and stratum spinosum layers of the epidermis.