Dvitamiinisynteesiä

Dvitamiinisynteesiä refers to the process by which the human body produces vitamin D. This vital process primarily occurs in the skin when it is exposed to ultraviolet B (UVB) radiation from sunlight. When UVB rays strike the skin, they interact with a precursor molecule called 7-dehydrocholesterol, converting it into previtamin D3. This previtamin D3 then undergoes a heat-dependent isomerization, transforming into vitamin D3 (cholecalciferol).

Following its synthesis in the skin, vitamin D3 is released into the bloodstream and transported to the liver. In the liver, it undergoes hydroxylation, a chemical reaction that adds a hydroxyl group, resulting in calcidiol (25-hydroxyvitamin D). Calcidiol is the main circulating form of vitamin D and is often measured in blood tests to assess vitamin D status.

The final activation step for vitamin D occurs in the kidneys. Here, calcidiol is further hydroxylated to produce calcitriol (1,25-dihydroxyvitamin D), the biologically active form of vitamin D. Calcitriol plays a crucial role in calcium and phosphate absorption from the intestines, bone metabolism, immune function, and cell growth. While sunlight is the primary source of vitamin D synthesis, dietary intake and supplements can also contribute to vitamin D levels.