Iodine is necessary for the synthesis of which hormone?(a) Adrenaline(b) Thyroxin(c) Auxin(d) Insulin

To determine which hormone requires iodine for synthesis, we can analyze the options provided: adrenaline, thyroxin, auxin, and insulin.

Step 1: Adrenaline Adrenaline, also known as epinephrine, is a hormone produced by the adrenal glands. It is responsible for the "fight or flight" response in the body. However, iodine is not necessary for the synthesis of adrenaline, so we can eliminate option (a).

Step 2: Thyroxin Thyroxin, also known as thyroxine, is a hormone produced by the thyroid gland. It plays a crucial role in regulating metabolism and growth. Iodine is indeed necessary for the synthesis of thyroxin, so we can consider option (b) as a potential answer.

Step 3: Auxin Auxin is a plant hormone that controls various aspects of plant growth and development. Unlike animals, plants do not require iodine for hormone synthesis. Therefore, we can eliminate option (c).

Step 4: Insulin Insulin is a hormone produced by the pancreas that regulates blood sugar levels. While insulin is essential for glucose metabolism, iodine is not involved in its synthesis. Hence, we can eliminate option (d).

Based on our analysis, the hormone that requires iodine for synthesis is thyroxin. Therefore, the correct answer is option (b) - thyroxin.