UV radiation is said to stimulate production of which substances?

• A. Corticosteroids and vitamin D
• B. Melanin and elastin
• C. Collagen and hyaluronic acid
• D. Keratin and keratohyalin

Answer: (A)

Exposure to UV light prompts the skin to produce vitamin D. This occurs when UVB converts 7-dehydrocholesterol in the skin to previtamin D3, which is processed into active vitamin D. In addition, UV exposure can trigger a local hormonal response in the skin, leading to the production of corticosteroid-like activity through POMC-derived peptides, contributing anti-inflammatory effects. So the substances that UV radiation stimulates, together, are corticosteroids and vitamin D.

Other options mix a correct response with an incorrect one: UV does stimulate melanin production, but the paired substance (elastin) is not increased by UV—in fact, UV exposure can contribute to degradation of elastin and collagen. UV’s effects on keratin and keratohyalin relate to epidermal structure rather than stimulation of new production in this context, and collagen/hyaluronic acid are not directly upregulated by UV exposure.