Synthesis of vitamin D in nature is dependent on the presence of UV radiation and subsequent activation in the liver and the kidneys. Many animals synthesize vitamin D 3 from 7-dehydrocholesterol, and many fungi synthesize vitamin D 2 from ergosterol. [46]

2021年12月31日 · Vitamin D 3 is produced in the skin from 7-dehydrocholesterol by UV irradiation, which breaks the B ring to form pre-D 3. Pre-D 3 isomerizes to D 3 but with continued UV irradiation to tachysterol and lumisterol. D 3 is preferentially removed from the …

Vitamin D (also referred to as calciferol) is a fat-soluble vitamin that is naturally present in a few foods, added to others, and available as a dietary supplement. It is also produced endogenously when ultraviolet (UV) rays from sunlight strike the skin and trigger vitamin D synthesis.

The epidermal layer of human skin synthesizes vitamin D when exposed to UV radiation. In the presence of sunlight, a form of vitamin D 3 called cholecalciferol is synthesized from a derivative of the steroid cholesterol in the skin.

Vitamin D is metabolized first to 25 hydroxyvitamin D (25OHD), then to the hormonal form 1,25-dihydroxyvitamin D (1,25(OH) 2 D). CYP2R1 is the most important 25-hydroxylase; CYP27B1 is the key 1-hydroxylase.

2020年7月20日 · Biologically active form of vitamin D calcitriol, like steroid hormones is synthesized in kidney. Calcitriol is synthesized in skin upon exposure to sunlight. Vitamin-D acts along with other hormones like parathyroid hormone and …

Vitamin D synthesis. Vitamin D undergoes two hydroxylations in the body for activation. Calcitriol (1,25-dihydroxyvitamin D 3), the active form of vitamin D, has a half-life of about 15 h, while calcidiol (25-hydroxyvitamin D 3) has a half-life of about 15 days.

Vitamin D is involved in the mechanisms of regulating the immune system; it regulates the actions of the suppressor T lymphocytes, the synthesis of cytokines, and acts by modulating the processes of cellular apoptosis [18]. Notably, vitamin D also stimulates the intestinal absorption of phosphate and prevents its renal excretion.

2025年2月9日 · Vitamin D, any of a group of fat-soluble vitamins that plays a role in calcium metabolism in animals. The primary source of vitamin D is sunlight exposure, whereby ultraviolet radiation converts sterols present in the skin to vitamin D. Learn more about vitamin D synthesis, actions, and deficiency.

2024年4月1日 · The primary source of vitamin D is the synthesis of cholecalciferol in the lower layers of our skin. This synthesis occurs through a photochemical reaction triggered by UVB radiation, either from direct sunlight or UVB lamps.