Which of the following hormones has the greatest effect on the overall metabolic rate in humans?

• A. Insulin
• B. Glucagon
• C. Thyroxine (T4)
• D. Cortisol

Answer: (C)

Verified step by step guidance

1. Step 1: Begin by understanding the role of each hormone listed in the question. Insulin regulates blood glucose levels by promoting the uptake of glucose into cells and its storage as glycogen. Glucagon works in opposition to insulin, stimulating the breakdown of glycogen into glucose when blood sugar levels are low.
2. Step 2: Examine the function of cortisol. Cortisol is a steroid hormone released during stress, and it helps regulate metabolism by promoting gluconeogenesis (the production of glucose from non-carbohydrate sources) and the breakdown of fats and proteins.
3. Step 3: Focus on thyroxine (T4). Thyroxine is a thyroid hormone that plays a critical role in regulating the overall metabolic rate. It increases the rate of cellular respiration and energy production by stimulating the activity of mitochondria in cells.
4. Step 4: Compare the effects of these hormones on metabolism. While insulin, glucagon, and cortisol have specific roles in glucose and energy regulation, thyroxine has the most widespread and direct impact on the overall metabolic rate by influencing nearly all cells in the body.
5. Step 5: Conclude that thyroxine (T4) has the greatest effect on the overall metabolic rate in humans due to its ability to regulate energy production and consumption at the cellular level.