On exposure to sunlight which vitamin is lost –
**Core Concept**
Vitamin D is a fat-soluble vitamin that plays a crucial role in maintaining bone health and calcium homeostasis. When exposed to sunlight, the skin undergoes a series of reactions that result in the production of vitamin D.
**Why the Correct Answer is Right**
Vitamin D production in the skin occurs when ultraviolet B (UVB) rays from the sun interact with 7-dehydrocholesterol, a cholesterol derivative, to form pre-vitamin D3. This pre-vitamin D3 is then converted to vitamin D3 (cholecalciferol) through a temperature-dependent isomerization reaction. Vitamin D3 is then transported to the liver, where it undergoes hydroxylation to form 25-hydroxyvitamin D, the major circulating form of the vitamin. The kidneys further hydroxylate 25-hydroxyvitamin D to form the active form of vitamin D, 1,25-dihydroxyvitamin D.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not specified, so we will proceed with the rest of the options.
**Option B:** This option is not related to vitamin D production in the skin.
**Option C:** This option is not correct as it is not related to vitamin D production in the skin.
**Clinical Pearl / High-Yield Fact**
Vitamin D deficiency is a common problem worldwide, particularly in individuals with limited sun exposure, darker skin pigmentation, or those with malabsorption syndromes. Vitamin D deficiency can lead to rickets in children and osteomalacia in adults.
**Correct Answer:** B.