Which combination of hormones originates from the skin and liver respectively?

• A. Skin: DHT, Vitamin D; Liver: IGF-1, TPO, Angiotensinogen
• B. Skin: Melatonin; Liver: EPO, Angiotensin II
• C. Skin: Estrogen; Liver: Insulin
• D. Skin: Progesterone; Liver: Cortisol

Answer: (A)

This question tests where certain hormones come from. The skin is a site for two hormone-related substances: dihydrotestosterone (DHT) and vitamin D. DHT is formed in peripheral tissues, including the skin, by the enzyme 5-alpha-reductase converting testosterone. Vitamin D synthesis also starts in the skin when UV light converts 7-dehydrocholesterol to cholecalciferol.

The liver, meanwhile, produces several hormone-related substances: IGF-1 (insulin-like growth factor 1) is made by hepatocytes in response to growth hormone; thrombopoietin (TPO) regulates platelet production and is produced by the liver; angiotensinogen, the precursor to angiotensin, is synthesized by the liver as part of the renin-angiotensin system.

Thus, the pairing skin: DHT and Vitamin D; liver: IGF-1, thrombopoietin, and angiotensinogen fits the origins described. Other options mix substances that are not primarily produced by skin or liver (for example, melatonin from the pineal gland; EPO from the kidney; insulin from the pancreas; hormones like estrogen and cortisol mainly from other tissues), so they don’t align with the origin pattern.