The primary growth-promoting hormone in the fetus is which substance?

• A. Glucose
• B. Thyroxine
• C. Insulin
• D. Human Growth Hormone

Answer: (C)

In the fetus, growth is driven largely by insulin, produced by the fetal pancreas. Insulin acts as an anabolic signal that promotes uptake of glucose and amino acids and stimulates protein synthesis, fat deposition, and overall organ growth. This makes insulin the main growth-promoting factor during gestation. Glucose provides the energy for growth, but it does not promote growth itself as a hormone. Thyroxine supports maturation and metabolic activity, but it is not the primary fetal growth driver. Human growth hormone has a more prominent role after birth, and fetal GH levels are not the key driver of fetal growth. A practical tie-in is that maternal diabetes can cause fetal hyperinsulinemia and increased growth, illustrating insulin’s central role in fetal development.