Vitamin D Precursor in Human Skin
The question asks for the form of vitamin D that naturally occurs in human skin before any conversion process begins.
Understanding Vitamin D Synthesis
- Human skin contains a precursor molecule that is converted into vitamin D upon exposure to ultraviolet B (UVB) radiation from sunlight.
- This initial molecule is a cholesterol derivative.
Analyzing the Options
- Option 1: Calciferol - This refers to Vitamin D2 (ergocalciferol) or Vitamin D3 (cholecalciferol). While Vitamin D3 is produced, calciferol itself isn't the initial precursor in the skin.
- Option 2: 7-hydrocholesterol - This is the correct precursor molecule present in the epidermis (outer layer) of the skin. UVB radiation acts on this molecule.
- Option 3: 25-hydroxycholecalciferol - This is an intermediate form of vitamin D produced in the liver after cholecalciferol enters the bloodstream.
- Option 4: 1,25-dihydroxycholecalciferol - This is the active, hormonal form of vitamin D, primarily produced in the kidneys.
Identifying the Naturally Occurring Form
Upon exposure to UVB light, 7-hydrocholesterol in the skin undergoes a photochemical reaction to form pre-vitamin D3, which then isomerizes to cholecalciferol (Vitamin D3). Therefore, 7-hydrocholesterol is the naturally occurring form in the skin that initiates vitamin D synthesis.
Important Questions from Vitamin D Deficiency
Consider the following statements with regard to Vitamin D deficiency :
1. Vitamin D deficiency is common in northern latitudes.
2. Vitamin D deficiency is more likely to develop in people with dark skin.
3. Exposure to UV light is advisable in patients with Vitamin D deficiency.
Which of the statements given above are correct?
Which of the following abnormalities occur from vitamin D deficiency in children?
1. Craniotabes
2. Bossing of frontal and parietal bones
3. Muscle hypotonia
4. Shrinking of epiphysis at the lower end of radius
Select the correct answer using the code given below.
- Which one of the following is not a feature of vitamin D deficiency rickets?
- Which one of the following is not characteristic of Vitamin-D resistant rickets ?
