Dvitaminszintézis

Dvitaminszintézis refers to the process by which the body produces Vitamin D. This vital nutrient is primarily synthesized in the skin when it is exposed to ultraviolet B (UVB) radiation from sunlight. The initial step involves a precursor molecule called 7-dehydrocholesterol, which is abundant in the skin. When UVB rays strike this molecule, a chemical reaction occurs, converting it into pre-vitamin D3. Pre-vitamin D3 then undergoes a heat-dependent rearrangement within the skin to form vitamin D3, also known as cholecalciferol.

This newly formed vitamin D3 is then released into the bloodstream and transported to the liver. In the liver, vitamin D3 undergoes hydroxylation, a process where a hydroxyl group is added, transforming it into 25-hydroxyvitamin D [25(OH)D]. This form of vitamin D is the major circulating metabolite and is commonly measured in blood tests to assess a person's vitamin D status.

From the liver, 25(OH)D travels to the kidneys. Here, it undergoes a second hydroxylation step, producing the biologically active form of vitamin D, 1,25-dihydroxyvitamin D [1,25(OH)2D], also known as calcitriol. Calcitriol plays a crucial role in calcium and phosphate absorption in the intestines, bone health, and immune function. While sunlight is the primary source of vitamin D synthesis, dietary intake and supplements also contribute to the body's vitamin D levels.